You can find pre-made batteries at
Angel Paintball Parts. You can also find some spare parts and o-ring kits there as well.
For chargers, see
this thread. The current recommendation would be the
CH-UN130 charger, or equivalent (unfortunately, I'm not sure of any sources in the UK, but if you can match up the specs you should be in good shape).
If you're looking for any specific parts, try checking the Angel Owners | OG Facebook group - I believe we have a few UK-based Angel owners in there who might be able to set you up with parts or at least point you in the right direction.