Converting a conservatory to single story extension

[Jim'llFixIt]

Hi
Excuse the username, my wife chose it.
We purchased a propoerty with a 30m2 conservatory built in June 2000. It is open plan to the house, but looses alot of heat.

Given the date the conservatory was built, would it be reasonable to assume that the foundations necessary for this build would be the same as those required for a single story extension = e.g. remove the glass windows and roof and add some brick/block work and put a timber and slate roof on? (subject to planning etc). Just thinking from a cost and time perspective.

Hope someone can help.
Thanks