For my pennyworth; I fly LGW-ABZ but have to use LHR T3/ T4 for long haul flights. LHR T1 is a disgrace and if I am transitting through there I prefer to take cabin baggage.
Its also a nightmare going from T1 to T4 to connect with a long haul flight which reminds me of another airport where this chaos occurs daily- that airport is Mumbai. Where does the fault lie? Its between BA and BAA. yet other airlines-such as bmi manage to get by.
Another post here has mentioned how bad LGW South is these days and I can vouch for that. I passed by yesterday on my way to the North Terminal and the security queue was snaking back beyond Easyjet's area. Having said that and felt smug for a few seconds, my face dropped when I saw the queue at the North terminal and this was just as bad. Then I had my flight with BA to round off a bad day... I'll have to take the risk and switch to bmi into LHR. Happy days.