When you're ready for the off, the boys or girls at F oaks will call TC for a joining clearance, presuming you've filed a flight plan along the lines of TF-CPT-L9-GD, requesting say FL80.
TC will issue a 'standard' non clearance of remain outside CAS call 134.12 or whatever and release subject Farnborough.
TF then call Fborough who will probably elect to give you a service after departure and get you pointing in the right direction before you call TC for your joining clearance (probably on track CPT climbing 6000/80) Fborough may have nothing in the way in which case call TC after departure.
In that case probably best to perhaps position yourself a little to the north of Fboro and well south of WOD tracking west to start with as direct track CPT will indeed put you nicely into the heathrow departures or indeed approach if it's easterlies.
Alll you then have to do is watch all those big whizzy things shooting past every window as they overtake you going west.