1. Part time is as rare as rocking horse !!!!!! Having kids or dependent parents is about the only way to get it and then only if the company have budgeted for it. A recent tribunal embarrassed management by revealing that even though they had invited bids for part time working they hadn't allocated any budget to it and so nobody was going to get it.
2. At LHR the bidding is in strict seniority order. You can bid for as many trip lines as you want at stage 1 or as many indiviidual trips at stage 2. It's all allocated in seniority order. Not sure how it works at LGW short haul, as they're on Carmen, not Bidline
3. The accomodation is for LHR pilots operating out of LGW. If you want it you have to ask, they'll assume you don't. If you are LHR based then trips out of LGW are rare on the Airbus. They are more common on the 777 but are also popular, hence slightly senior.