An innocuous and reasonable question - but one which poses even more questions!
First, in Glasgow you'd need something like a 60cm Dish for best results.
Second, there are several different approaches to reception:
1. Freesat (Branded Receivers from places like Currys, Argos, John Lewis etc.) - You can also opt for an Installation package.
2. FreesatfromSky - specifically the Pay Once Watch Forever Package, also available from eg Currys, Dixons. This is just under £75 inc. Box, Card, Installation and also gives you (for free) two Subscription Mixes of Channels for a few months. No obligation to subscribe afterwards.
3. Generic Receivers (Not specifically related to any Platform) - available widely! ie Some shops like B&Q, Maplin; Loads of Internet Suppliers (some of whom are also Sponsors of this Forum); eBay (of course). Dishes, LNBs etc. also from the same sources.
You also need to consider whether you are happy just to have Standard Definition Channels or whether you want High Definition and also give some thought to whether you think you might want to look at stuff other than UK Channels.