Yes, basing is often dictated by the rules you intend to use but also by the type of game you want to play. Do you want to play 'big battles' or skirmish games, for example?
Skirmish games (rules like Sharp Practice or Brother against Brother) usually need individually based figures - I mount mine on 1p or 2p coins, depending on the size of the base (I see you are in Lowestoft) and then use movement trays from Warbases as proxy stands when I want to play larger games.
Which rules you use for large battles (Fire & Fury are one of the most popular for ACW in the UK) is also dependent on what your opponents/local club are accustomed to using - and if you're just getting into the hobby, joining a local club is a great way of picking up the basics.
I've not visited them, but I hear good things about the clubs at New Buckenham and the Coltishall Cowards near Norwich, both of which have a strong tradition of historical gaming (rather than Games Workshop type 'fantasy')games). Both are easily googled.
Let us know how you get on!