fireflybob, you're talking bolleaux. The TL is based on the TA which in the UK is predominantly 3000ft (or some other figure depending upon whether you're below various bits of CAS). The TA is based on aerodrome QNH which, spookily, is derived by formula (ie it isn't necessarily an accurate figure) from the QFE. Despite best efforts, most airfields don't dig a bleedin' deep hole down to msl to drop a barometer down
)
Good reason for QFE
LiveLeak.com - Thunderbirds Ejection, how it happened.