Welcome to Flyertalk GabrielExea, welcome to the BA board. It's good to see you here, and thanks for the question. The TP run thread has become a little unwieldy perhaps but if you delve into it you will see some London based TP information. But welcome on board, if you keep an eye on this board for a few weeks you will soon pick up lots of snippets that will help.

I think there are 5 core mechanisms:
1) CE weekends to places like ATH, IST, HEL and MLA, these get 80 TPs in CE each sector, so 160 TPs return, no need to for clever routings so long as you spend the Saturday night at the destination. And many of the destinations are worth a visit. LGW is generally cheaper than LHR.

2) Clever routings such as the JER one mentioned by our composer friend.

3) Buying EuroTraveller on a route where you may get a Pro Active upgrade (POUG) to Club Europe, alternatively the version for sale in airports on the day of departure, Airport Upgrade Promotion (AUP) - bit risky because you may not get it, but there are some fun places worth visiting to find that out!

4) BA Holidays, can be a bit random this, but if you book a hotel and flight package you can get some stonking value (e.g. ET to Sofia for £167 return including 2 nights in the Ramada). You can either AUP that, or buy straight into CE on BA Holidays, there are some good prices to Dublin in the winter for example.

5) For a few TPs, £39 hand baggage only fares to places like BCN, EDI, NCE are good value, and though you only 10 TPs, that's still better for money than most fares! A variant of this are promotional day return fares you will find on ba.com for weekends.