Boilermate II Replacement : Is a straight swap of an Ideal Classic boiler possible?

Can anyone offer advice on the easiest replacement for an Ideal Classic boiler if I replace the Boilermate II with an unvented cylinder (MegaFlo or similar).  I don't want to have to rip up the kitchen.

I only have 15mm gas pipe to the area where the boiler is so I guess the replacement will have to be a Vaillant?  The Ideal has two 22mm flow/return pipes that lead to the Boilermate that I would want to reuse.  I do not want to have to run any other pipes to the boiler area.  Can this be done?

Many thanks.

Baxi Eco blue advance is pretty good.
Only needs switched live neutral & earth.
Your gas supply needs checking.
Depends on how far away from the meter.
And gas hob, oven fire etc.
Mike