How difficult/expensive would it be...

[ShoeWhore]

To get rid of a conservatory? Or a detached garage?

Don't know about a conservatory.

We just sold our detached garage which was a pre-fab with asbestos roof for a few hundred. So depending on the construction you may be able to make money.

Do not get rid of anything if you do not have PP to replace it. Vital in green belt and AONB areas. We have had a conservatory demolished but it was part of a much bigger building scheme so I don't have an individual cost. Any general builder could easily give you a quote.