Hi Lokas,
Shifts - depending on job (I've been in about 4 departmrnts) but all pretty much Earlies, Lates and Nights. Earlies can start between 0445 and 0600, Lates from about 1400 ish depends on the cover required. We also have Day shifts (12-13 hrs) but not sure if the LHR boys and girls have these (again could vary between departments). days on and off again depending on area some do 5-3, 6-3 or even 4-4 (rare).
It seems to me that most of the interview questions revolve around teamwork, leadership etc, but it would pay to have some knowledge of the company and the operation, have a good look at ba.com.
When I joined ('98) I had to do a few tests before being invited back for interview - numeracy, logic, spatial awareness etc not really stuff you can revise for unfortunatly. Was then invited to return for an interview and when succesful at that was offered a job pending medical and BA driving test (landside only on the public highways). My airside test came later when I moved to another section of Cargo and needed to go airside.
Also I am sure you would have been told that the employment is dependent upon 5 years checkable history and criminal record checks.
Hope this helps,
Regards Bluejay