Hi - just completed my LGW training - we were provided with hotel accomodation whilst training at LHR and BA bussed us to LHR and back to LGW each week. We also got training allowances which helped bump up the wages
We were at LHR Wednesday, Thursday and Friday one week (2 nights in hotel) then back the next Monday through to Friday (4 nights). You get a daily allowance for both training days at LGW and also at LHR.
Good luck for your course - back from my 777 supernumerary this morning and loved every bit of it - looking forward to the mix of long and short haul flying and the crews I have met so far are brilliant!