Welcome to the forum!
As already mentioned, Glasgow Airport is horribly expensive.
Prestwick is excellent. I pay £26 for landing and a day's parking in my SR22. The flight centre there are excellent and Avis will deliver a rental car there if you ask the office at Prestwick directly (they do so regularly for me).
They also have ILS if the weather's bad and a cross runway if Gertrude's crosswind strikes
Cumbernauld is also excellent with lower landing fees and parking but no IAP (you can use the Glasgow ILS for cloud break) and no cross runway. I don't know about onward transport from there as I've always been met when I have flown there.
I hope you have a great trip!
