Just note that reception varies depending on the type of dish, LNB (and feedhorn) and in some cases the receiver used. For example a good quality 80cm dish, low noise LNB,high quality cabling and properly terminated connections can easily outperform a budget 1.5 meter dish, noisy LNB, budget cabling and improper termination. Channel Master, Funke and Triax are known good dish makes. Invacom 0.3dB and MTi 0.3dB are known high quality LNBs. When choosing cabling, ensure you get high quality foam filled cabling to avoid any chance of water running down in the middle.
Also, if you plan on getting a 2nd hand dish, be sure the dish is in good condition and if it is a prime focus dish, make it comes with its original feed horn. A dish's own feed horn is designed to 'see' up to the circumference of the dish, where as universal replacement feedhorns may only see a certain portion of the dish, or may even see beyond the edges of the dish and thus pick up stray radiation. Finally check for dents or warps. A large dent can reflect stray radiation (such as from another satellite) on the LNB and thus degrade performance. A warped dish (even if very slight) will not tightly focus the radiation onto the LNB properly.
Just be warned that if you do plan on taking up a Sky subscription, you will need someone in the UK to do this and get them to send over the box. Sky will not offer subscriptions to those outside the UK or Ireland. Also, any features that require the box to be connected to the phoneline will be unavailable.