To try to answer some of your questions:
Initially there will one extra sector working alongside the present 125.250 person. Frequency is to be allocated, but don't be surprised if it sounds familiar. Farnborough already has access to two radar heads at Heathrow plus the Pease SSR head (sited south of Gatwick). It's probable the Stansted primary will be added to this tally, plus maybe Debden SSR.
Transponder codes are in short supply; Farnborough already has use of much of the 04XX block and maybe the rest could be allocated. But don't be surprised if an aircraft at (say) Basingstoke is allocated the same code as one at (say) Thurrock.