Loft conversion, old boiler/cylinder and new bathroom advice!

[madamy]

So, we are in a traditional 3 bed semi and want to do a loft conversion to make a 4th bedroom. Maybe with an en-suite. Plenty of room/headspace up there so no problems with that bit!
However, we have a cold water tank and hot water cylinder contraption up there - looks like a space ship - and an ancient old boiler in the downstairs cloakroom. I'm assuming this will all need to come out and our ancient boiler be updated.
We also want to completely redo the family bathroom and put a decent shower in. We're at the top of a hill and our current shower is pants - not sure if that's anything to do with water pressure?!
Does anyone have any idea on which bit to do first? We're a bit reluctant to do the lot together due to the upheaval - mind you we could stay with my parents for a while - but then have no idea how we'd co-ordinate.
You may gather that this is all quite new - not had major work done anywhere before so feel a bit out of my depth!

I'd be thinking about an unvented cylinder (runs at main pressure). Megaflo is one brand name.

To make it work properly you will need good water flow and pressure into the house, which usually means replacing the old service pipe to the pavement with a new, larger, plastic one, and continuing the larger pipe all the way to the cylinder and bathtaps. It's important that the pipes are not throttled with small valves or sections of small pipework. The large valves are relatively expensive so some plumbers will fit small ones. 32mm pref but 25mm will do.

Running the pipe out to the road will need a trench. Builders will do that. Plumbers are weedy fellows. It need not follow the same route as the old pipe. Ask your water co to test your drinking water for lead content as there might be a subsidy, or free reconnection. Ask now as there could be a long delay, and it must be completed before starting work.

You will need a good local plumber, by recommendation, who will be familiar with the job. He has to have a G3 qualification, not all heating engineers do.

It's possible to continue using the old boiler but this might be a good time to replace it. You need a heat-only, conventional or system boiler, not a combi. Opinions differ, but it may well be more reliable.

Yes to probably replacing your service pipe. But you can get a company specialising in moling to do it and they only dig a hole every 10 metres or so and font have to dig up your driveway. Ours in greater London cost about £1200 for around 30m and took half a day. This can be done seperately to other jobs. We did get rid of our old tanks (one on first and one on second floor) as well and did end up getting a Worcester Bosch combi boiler and needed to replace the existing power shower because of it. For us we haven't changed the layout of the family bathroom so it didn't matter that it wssnt renovated. Just had holes in the wall for two years where old shower was. If you are going to change layout then you should probably do this all at the same time. You should be able to plumb the loft later. I think your best bet is get a plumber round for your situation and know your plans and they can discuss the order of doing things. FWIW you could do loft before you do family bathroom so you have something to use while the other is getting done.