Lessons learned for me. [waves to Soberton] We also did a bathroom and two beds in a Victorian terrace, needing the first floor ceilings lowered.
Current building regs for insulation will still result in a loft which is cold in winter and too hot in summer. We had another tradesman in the house who recommended (too late) that we should have also lined the walls with ply. The 4-6in celotex stuff was not enough. The ply would also give a firm base to hang radiators on etc etc. No idea if it would have made a huge diff to the insulation as we had missed the boat so def worth researching.
We put in top hanging velux windows (not hinged in the middle) to avoid bumping your head on them when open. You can't put a security/child lock on top hanging windows though. They are often put in as a fire escape method so I guess that's why Velux don't offer it. The windows will blow open to the max though in a stiff breeze so it's a pain, aside from the safety aspect if you've got children up there.
The stairs although wide curves onto the landing. It's difficult to explain but in practice, it would be very easy to slip down 4/5 steps if you took a step backwards on the corner by the handrail post. Not an issue for adults but with small children its been heart in mouth a few times as there isn't the right constructino to put a stair gate on there. Visiting children or folk in the night are a bigger concern. We didn't put an electrical socket on the tiny landing which was a mistake. A) it's somewhere quick to plug in the socket or wifi booster B) it's a convenient place to put a plug-in safety light.
Yes to velux black out blinds. They are great but pricey, def budget them in.
We have sash windows on the dormer on the back to keep the look of the rest of the house. Mistake. Impossible to clean/get cleaned and they need security locks on them too to stop kids falling out. You can get sashes which open on the side for cleaning but they are mega bucks I think.
We put in a flat roof window dome like this above the new stairwell.
www.velux.co.uk/private/products/velux_roof_windows/windows_for_flat_roofs
It's worth putting the largest one you can fit as it floods the whole house with light. Insist on a brand that you can put an electronic blind on so you can control the loft temp better.
Our loft company wanted to put the bathroom in the dormer side only. It couldn't be done to put it elsewhere because they need to slope down the waste pipes and we were v tight on headroom. So we got a plumber ourselves who was prepared to run the waste pipes from the new bathroom, drop into a bedroom on the first floor (well insulated against noise) and out that way. Main loft bedroom is much bigger as a result.
We moved a combi boiler to the loft. Both the loft bathroom and main bathroom have great water pressure as a result and there is no significant delay to the warm water in the kitchen. We had to replace the boiler anyway but they are expensive to relocate so worth getting a fixed quote for this. There are regs around the loft windows and the pipes for the boiler so you may have to compromise on the location.
We insisted they couldn't use chipboard to floor the loft as apparently it starts to squeak horribly after a few years. Also the whole board has to come up if there's a problem under the floorboards (waste, electric lights for rooms below etc etc) or cut into which is even squeakier in the long run.
Plan the rooms carefully for storage. We didn't line the rooms with ply, so the radiators are hung on wall joists (don't know the correct term). In order to hang them, the radiator is now too far in one direction to fit in an under eave wardrobe. Still figuring out how to get around this without replumbing in the rad.
Lowered the ceilings - we had to empty the rooms below including all carpets and underlay. It looked like a bomb had gone off in those rooms, 100 yrs of victorian coal dust and dirt. The walls wobbled and there was no lighting as no ceilings lights left. Man it was cold, cold, cold. Took about a week for the steels to go in and plasterboard to go up but no plastering or electricals for weeks so you can't really move back into those rooms in any real way.
You can buy rolls of sticky plastic to protect floors. Looks like a giant roll of sellotape. It's the business for sealing off the doors to rooms you want to keep dust free (ish anyway). You can rip it down at the end of the day, bin it and hang a new drop in the morning.
You'll end up replastering/redecorating most of the house. Once you start doing that, you'll add more cost because if you are sensible you will take the opportunity to upgrade old wiring, or add sockets etc. Plan a LARGE contingency fund.
We put most of our house into storage and lived out of the kitchen and dining room/one bedroom for DD for 8 weeks. Declutter like you have never decluttered before unless you like drycleaning bills to make your eyes water.