Mr Punter

Is this stuff just plastic?

It is to strengthen the brickwork. Try demolishing a wall with brick reinforcement and you will see. A bit like reinforced concrete v not.

Please shut up about radon. It is low where you are. More chance of being run over by a milk float.

They are not eating the wood, just using the fibres to make nests. If it is coated you should not have any issues as the wasps like the weathered stuff.

The paving may still shift about as the ground swells and shrinks. Not much you can do on a domestic patio.

I have seen the plinth seals that wrap around the bottom edge. They are friction fit and could be replaced. They are probably a better solution as you don't have to rout a groove.

Just look around for trees. Even if they are small you need to treat them as full height. Hawthorn, Oak and Willow are big drinkers!

They can be expensive as well!

With the over fascia vents the airflow comes up from underneath. The plastic eaves membrane support trays are better than bitumen but either should be fine.

There is sometimes quite a lead time on wind posts. How many have been specified? Somewhere along the line you will need structural drawings and calcs that comply with part A. You can normally bolt the windposts to the slab or concrete them in. They add a surprising amount of strength and stiffness to a wall. The alternative could be some brick reinforcing - like train track in the mortar beds - but I don't know if it will work for your design.

It is not bad, just very unpleasant to breathe in, stings in cuts and eyes, dusty. Much more volume than cement. It does make the mortar nice and creamy and workable though. I wouldn't cut the bag in half.

You get almost no suction on the marmox type boards. The foam core is XPS and completely waterproof.

I would say the biggest risk to colour variation is what sand and cement you use so having all the sand in one load is good. Make sure the cement is the same make and supplier throughout. I have used some that was very inconsistent in colour. Shovelling lime into a gauging bucket before chucking it into the mixer is a horrible job, but they should have paid more attention at school.

We have got the bricklayer to include a slate course in the past where we needed to work the coursing in with a steel on one wall. The could have gone for a cut block but the slate was simpler. For your 26mm you could have 6mm slate and 2 x 10mm joints.

If the ground investigation is decent they should be able to get a good idea. Also access and proximity to adjacent structures can have an impact that the piling contractor can factor in.