Ace Rimmer - the reason the easy TLS flight was more expensive than the BA flight is that it is nearly sold out. You were looking at one of the last 25 seats on the aircraft.
I can't comment on how full the BA aircraft was at that point but it does illustrate that spot comparisons between airlines is rather fraught. Yeild management fluctates quoted prices wildly and (seemingly) randomly over time.
The fact that easyJet at Gatwick are booming is a far better indicator that the punters like the product.