Both fleets working very hard now, 737 does (I think) about 800 hours per years with Airbus on 750ish but rising.
Rosters are bid for on both fleets. LHR uses Bidline which, with seniority can guarantee you days off. LGW uses the inferior Carmen system which is a bit more vague. Management would sell their mothers rather than introduce Bidline to LGW.
Yes. Absolutely.
No, unless they are midweek. Preferences can be expressed but more often than not are ignored. Really important days can be requested from the management but generally they've got to be along the line of some sort of compassionate requirement, in which case they're pretty good.
Airbus has nightstops galore. LGW has about 5 or 6.