To the OP, we've just replaced our Baxi Solo 26-Year Old Boiler with a Baxi EcoBlue Advance Heat 25KW Boiler, Didn't want a Combi, as we have a £1K Aqualisa Pumped-Shower which is the only one I ever use in the house......
And as you can see from the photo, it needed to go in the space vacated by the Original Baxi.....
It was recommended by our Boiler Guy, who did a really cracking Job.....Rear Flue needed a Flue Kit as it wasn't to the current Regs....Of Course the Feed & Return plus Gas Pipes needed to be cut to suit....But all went swimmingly....
In fact If you would push me, I swear that the Rads & HW are hotter than with the Old Baxi, The only thing I have left to do, is to fit a Nest 3rd Generation thermostat....Which I'll try & fit once I am confident enough that the Boiler is working well 4 a few weeks, so that I won't be introducing any other faults when fitting it.....