Loft insulation, half boarding out and loft ladder fitting

Jet

I am really struggling to get quotes for this. I have contacted so many people and only obtained 3 quotes.  Small 3 bed semi in the south east.  Current insulation about 50mm, I would like this topped up and around half the loft boarded, so I can store things and a loft ladder installed so I can access the space properly.

The first guy said he thought I should just insulate and then squash it down with boarding and "worry about the (possible) damp" later.  He also didn't want to touch a structure in the loft that used to house the old water tank meaning climbing round it every time.  He also didn't want to quote for the loft ladder as I suspect he didn't know if it would fit etc. £620

Second guy seemed much more professional and more re-assuring.  Said I needed a bespoke loft hatch made, he would remove the water tank structure and raise up the boarding so it didn't squash down the insulation.  Also mentioned about removing waste, which the first guy didn't mention.  £1820.

Third guy didn't even visit my property, he asked to be sent a video.  Quote mentions cutting out new loft hatch and fitting new architrave. No mention of removing water tank structure.  Will raise floor with loft legs.  Will leave all rubbish for me to clear. £1435.

I liked the second guy best, but don't like his quote!  Is it fair though?

FreeBear

What level of insulation were they suggesting ?

300mm is the minimum you should aiming for in my opinion. Depending on the size of joists up in the loft, you might get away with 175mm legs. Or if like me, you have weedy 75x50mm joists, 300mm legs would be needed (not much difference in price).

First guy - Wouldn't bother with. He clearly doesn't understand the importance of loft legs to avoid compressing the insulation.

Second guy - Sounds a bit on the expensive side, but boarding a loft is fiddly work, especially if using legs.

Third guy - By the time you've paid for waste disposal, you won't be far off the second quote.

Jet

Both 1st and 2nd guy are saying 200mm of insulation, 3rd guy is saying 170mm.  My understanding is that any more than that will mean a very big step into the loft,

FreeBear

Assuming fibreglass or mineral wool, minimum recommended level is 270mm to get to current Building Regulations target. You can reduce the level by using a higher performance material such as PIR/PUR board (e.g. Celotex), but it is difficult to fit effectively within a loft space and quite a bit more expensive.

My loft hatch is very close to the hip roof, so head room is extremely limited. That hasn't stopped me putting down 300-350mm of insulation across most of the loft space and boarding out the central area - Used 300mm loft legs. In the area close to the hatch, I'll be using Celotex between & on top of the joists with boards resting on top (no legs). As Celotex has twice the insulating effect of fibreglass, only need ~150mm to hit the required u-value.

Adding an extra 100mm will increase material costs by ~£3 per square metre, but won't add much to the cost of labour. If you want to avoid the "big step up", reduce the level of insulation adjacent to the loft hatch as described above.