Mr Punter

Do the gas network have any easement or wayleave? When you bought the property were you aware of the gas main on your land? Service plans are rarely very accurate. If it is shown on your land the location can be very approximate and as you say, it is easier to soft dig than to remove / replace flagstones. If you want it done quickly, contact the emergency number and say your groundworker has just hit a pipe and you think you can smell gas.

Unless this is 4 storey plus, brick / cavity / block construction gives adequate fire resistance. The cavity is not strongly ventilated enough for the chimney effect. The weepholes may allow an external fire into the cavity, but the building would likely be compromised by then in any case.

OK Consider ripping out all the timber and sleeper walls, compact the sub base, stone / crushed concrete. Insulation then concrete or concrete, insulation, screed or chipboard.

If you have a ceiling height of at least 2350mm and you would be willing to lose 50mm, you could consider adding 30mm Celotex insulation on top of the floorboards with 22mm t&g chipboard on top. This will make a huge difference compared to an uninsulated floor. You would need to cut the door bottoms and remove the skirting and either replace or refit.

2 bits of drainage can be tested: below ground can either be blocked at the lowest chamber and filled with water to see if the level drops, or block off individual pipe runs with an air test. Inside pipework is also needed to be air tested. All the test details are in the Building Regs Part H. If you used a plumber, they should be able to help. Even if you didn't you may want to get one in to test the system for the Building Inspector to witness (normally test first to make sure it is OK).

The void under a timber floor should normally be ventilated to the outside via airbricks. This stops moisture forming under the floor. I would not have thought that cold bridging from the joists would make much difference.

Looks very posh for a Crossfit!

Maybe see if BC pick it up. They really should but I often see stuff which doesn't comply. Not sure if they were modified after BC final.

It may be best to ask the supplier / manufacturer / designer as it should be their responsibility for the design / spec.

They will look at mechanical ventilation, smoke detectors, opening windows, 100mm gaps to stairs and want to have access to Gas, Electric, EPC / air tests and will often want to witness an air test of the waste system. Sometimes they can just get a couple of things that everyone gets caught on - like locks on escape windows or thumb turns on escape doors or spy holes.

OK but I would not cut into the neighbours sewer line - just put in a new IC and connect this to the brick IC

It should be fine if you add in the extra chamber before the final one. Who is Bb?

That is because it is shown from the outside in plan view, where the glass covers most of the frame. If you look at the sections it is fairly clear and the dimensions are to the outside of the frame and the frame covers the upstands. On the basis that you need some more windows, find out the MINIMUM they are prepared to charge, then perhaps do a letter before action saying what you are prepared to accept. That will put you in better standing at Court, as you have made a reasonable attempt to negotiate a fair settlement. Keep all correspondence civil.

Did they send a dimensioned drawing for each window? The drawing you posted earlier gives a dimension showing the overall window size. If you agreed that these were correct you may be on sticky ground.

Did you sign the drawings? If so, just try to negotiate. If not, claim that they should have worked to the structural opening sizes supplied by you and that you considered that the drawings they sent were only indicative of a standard detail and were not being relied upon for finished window sizes.