Reckless Rat

There must be someone out there who has a newish condensing type boiler?
We've been recommended a new replacement boiler (Glow Worm) to be fitted in the garage (original Potterton in the Kitchen) and we've been assured that the heating of the garage from a new boiler install is minimal.
Problem is we have a pair of tortoise hibernating in the garage and bringing them out of hibernation due to a temperature rise could be fatal.
The old boiler in the kitchen puts out quite a lot of heat, with the casing being too hot to touch for long when it's running.

Can anyone confirm what we've been told?

Thanks!
RR