Boiler placement?

[Monkfish]

We currently have an old (30 years) natural gas boiler downstairs solely for our central heating and an electric immersion tank upstairs for baths and showers etc.

If possible we would like to install a new combi condensing boiler in the location of our current immersion tank (upstairs).

Would the current regulations permit this?

The back of the airing cupboard in which the new boiler would be situated is an outside wall so installing a vent should not be a problem.

This would free up space in the downstairs cloakroom where the current boiler is situated and allow us to convert that into a downstairs toilet.

Any advice would be greatly appreciated.