Try searching this forum for "OASC" - you should find plenty of info there.
Aircraft recce - you need to be a bit more specific. If this is for OASC prep, then you don't need to know that much. Just read up on the current RAF aircraft and future prospects (UAVs included). Best site for that is the RAF website - more detail than you will need. Also BBC News website is worth a search - you can find information about new UAV developments and current kit.
If you just wanted general advice about air recce, then the best way of learning aircraft is to buy Janes Aircraft Recognition Handbook. Also, you may find that if you regularly read Air Forces Monthly or similar, just by reading about aircraft regularly you will pick a lot up.
Finally, recce is best learnt by looking at both similarities and differences between confusable aircraft.