If you need an extra core for a pump overrun sometimes if existing programmer is by boiler and wiring centre is in the airing cupboard you can move the programmer to the airing cupboard, then you've got an extra cable to play with.
Also, try and get your head around the sequence of what does...
does seem strange to have the Rehau wiring centre for the UFH and then only have 1 zone on it. If it was only ever going to be set-up to all come on at the same time they could have done it without that expensive wiring centre and done it with a 10 way terminal block wiring centre.
depends on the make of lockshield surely though as a lot are different, a lot of the time you can use a head of a manual wheel head valves though, perhaps keep a selection instead of scrapping them.
concrete will eat through hair felt lagging, ive replaced alot of copper before where its been in hair felt lagging and concreted over and eventually pinholed through.
what make is it, there designed so everything can be changed though the square flush plate once removed.
P.s its not a grohe one is it...rapid sl? as they have a brass isolation valve inside the cistern you undo with a flat headed screwdriver and they come closed from the factory.
Ive got the 180mm and the 250's, i now use the 180mm ones all the time, great for 15 and 22. The 250mm ones i rarely use, feel a bit awkward on 15mm stuff, fair bit heavier than equivalant size bahco spanner or cobras.
also having 2x domestic boilers cascaded together rather than 1x commercial boiler means spares are easier to get hold of plus more chance of a heating engineer knowing what there working on...
good luck and godspeed
The return on the cylinder should be the last tee before it goes back to boiler to avoid reverse circulation when just DHW is called for.
I hope the cylinder is vented and not unvented if its coming off that 3 port valve...post some pictures up if you want.