I am in the process of moving my hot water tank from a cupboard in the
bathroom to a fitted wardrobe in the adjacent bedroom. There is
currently a back boiler in the living room chimney.

In terms of planning ahead I would like to allow space in the wardrobe
to fit a conventional boiler at a later date when the back boiler
finally gives up and dies. The flow/return for the boiler passes under
the bedroom which would make it easy to re-route later on. One side of
the cupboard is on an outside wall which would allow for flue
installation.

My question is whether it's feasible to have a hot water tank in the
same cupboard as the boiler. A quick look at a couple boiler manuals
suggests that there are specific ventilation requirements for boilers
and it is quite likely that another heat source in the same cupboard
would not be permitted.

I don't plan on fitting the boiler myself, just wanted to make it easy
to install one later on when the time comes.

Don't want to go down the combi route so please don't suggest removing
the tank and fitting a combi!

Any help is appreciated.