Mr Punter

I would concentrate on improving the cottage. Insulate and improve airtightness. Control ventilation maybe with MVHR. In many ways this is much more of a challenge than new build.

Give the ICF firm a call and ask them the best (quickest / cheapest) way to get over slightly uneven foundations. They will be most amenable. 50mm is well within tolerances for foundation concrete.

LED strip?

We paid £20 per metre for single skin blockwork, £65 for cavity wall with facing brickwork. Lintols and padstones £16.50. I would have thought that you can get blockwork done for between £15 and £30 per metre labour only. Get a price instead of day rate, even if it just a price per meter or block, so that you can measure when he wants paying.

Do you know which ones are threaded half way? Screwfix tend to show the same pic for all lengths and mostly the shorter ones are fully threaded.

We are fixing some 18mm ply down onto 22mm chipboard in bathrooms so we can finish with 2.5mm Luxury Vinyl Tile and the finished level will match the oak floor on the adjacent landing. I was thinking of screwing this down, but we can't get many fixings into the underlying joists, so I would like to just screw into the chipboard using 38mm screws. Can I get these threaded half way, so the ply does not get jacked up by the screw? I will be needing a fair few.

You can get a lintel 100 x 140 x 1200 like http://www.builderdepot.co.uk/concrete-lintel-textured-pre-stressed-100mm-x-140mm-x-1200mm.html which may be sensible for supporting the floor above. Engineering bricks are http://www.builderdepot.co.uk/class-b-engineering-brick-smooth-red-b101.html

As it is only a 65mm lintel (are you happy it is man enough?) you can just use engineering bricks for the ends. As per @ProDave acros and planks.

Tamping will be fine. You need to try to get the concrete to completely cover the rebar, to prevent rusting / spalling, but this is v. unlikely to be an issue with foundations below ground.

New build with timber ground floor, so partially propped. Chose Polarwall as it is flexible and simple to construct. Waterproofing was concrete admixture plus type c internal drained cavity, sump and pumps. Ground was chalk and putty chalk. Polarwall materials were £5,600. Area was 66m2 internally but including a light well - before we added the internal wall linings. We also had slab, mesh, temporary works (augered and king post walls) and additional insulation. In total the basement structure alone was £56,000, waterproofed and insulated.

I have done an icf basement. Used Polarwall with 300mm concrete core reinforced with mesh. You will need at least 800mm of working room around the outside. Potential issues are Party Wall notices, Means of Escape, ventilation, daylighting, excavation and temporary propping / shoring, engineering design and calcs, waterproofing, warranty guarantees and final value v. value of above ground floor space. As you are a novice on a tight budget I advise that you steer clear of a basement.

Why the battens?

Birch have a low water uptake and so not too much soil shrinkage / heave. Beware willows and leylandii.

The most practical solution may be to have a small triangular fixed light in the bottom right corner and a narrow door to the left. This would mean that you do not need so much space inside / outside.

Maybe easier to create a new opening to the left. What is the grey cladding btw?

Some of these were 4 storey without an alternative means of escape, other than the main staircase. They share a 50mm main supply, split off to 32mm for each unit. No pumps or accumulators. Interlinked mains smoke or heat detector in all habitable rooms and stairwells. In the event that one of the heads is activated, the water released is nothing compared to that from a fire tender.

I have had issues with these screens. I no longer spec any shower screens around baths as they can lead to callbacks.

I tried to spec the Keystone Hi Therm lintels, which have a thermal break and a much better Psi value. Lead times made them impractical though.

I have just had sprinklers installed in 7 houses. Total cost £16,950 to cover 1183m2 total = £14.33 / m or £2,421 per house. Mains fed.

I would have thought the radon barrier would be all the DPM you need. Not sure what the others are for. How are you fixing the sole plates?

The B & B floor should help if it restrains the walls. I have done an ICF basement and had a similar spec, with chalk soil. I think you could end up spending more on engineer costs than you save in mesh. I don't think you will get away with fibres either, but it is worth asking. How are you waterproofing?

The frame will shrink but the blockwork will not. At first floor level this means that if you initially have, say a 10mm gap around your blockwork at head and cill, this may, after a couple of years, become 22mm at the head and -2mm at the cill. This has a much larger effect the more storeys you are, so on the ground floor allow for 3mm and 9mm per floor above. To compensate, leave a very tight gap at the head and a large gap at the cill. Use an external sealant such as Illbuck Timbermax tape, which will take up the movement without compromising weather tightness. Leave enough of a gap at the eaves so that the roof does not end up sitting on the blockwork after the frame shrinks. Completing the roof covering and loading plasterboards help the frame compress. If you have a cladding or tile hanging system fixed to the frame much of the issue is eliminated.

I see no reason why not. If the windows are the Velfac type - sash is flush with frame - you may even need to render the reveals and heads before the windows go in. Make sure you account for the frame shrinking 12mm per floor - both with regard to windows and roof. It is worth clarifying the cill, head and reveal details early on so that the bricklayer can build to the correct spec.

@PeterW's best suggestion was to lose the hollowcore on the first floor. His others were good too.

We used a timber plate with coach screws into the back instead of the polystyrene to cast into the concrete on the inner section of the Polarwall and face fixed hangers to this. I am sure there are other methods.