What is above the branch? a strap on boss will work, but a bossed pipe is better. It looks from the photo that the waste pipe is push fit, so different size and plastic from solvent weld.
Hi Jon, just had a quick look on the Honeywell site and it seems you can upgrade to the Evohome system.
Will need full details of your heating system to be certain if it is compatible
Your cylinder thermostat is probably just a bi-metal on/off switch, where as the Evohome will monitor the...
Depends on how much time and money you want to spend, but a botched job could make for problems later. If it's only 3 to4 inches thats a near miss, always hard to fit. Cut soil flush to wall, chisel around soil to make enough room to slide on a 45 socket of a 45m/f (chamfer first and grease)...