Is life really that bad as a junior FO there?
Not necessarily. It depends which fleet you end up on and what your particular interest is. On the 777, you will do five or six trips a month (mainly Eastern Seaboard or Saudi). On the -400, you will do 4 trips a month (very similar trips to the 777 except you will get one 'seeded' trip per month - ie. JNB or LAX). On the short-haul fleets, you will work hard although destinations are less relevant, however you will have to compromise your whole month to achieve a specific day off (as is the case with longhaul). In all cases, you will work a lot of weekends. As your seniority increases, your lifestyle will improve. At my level, I achieve either decent trips or 95% of my desired days off, not both. In the top third, you would probably achieve both. There are likely to be very few places available on the -400, although a large number are to be recruited onto the 777. BA is now advertising for Self Sponsored pilots, who would almost certainly go onto the Airbus or the 737.
The only drawback is that if you join now, you're likely to remain junior for a lot longer than perhaps you would have done in the past. Personally, I have been in seven years and I'm a third of the way up the seniority list, as I joined at the start of the retirement bulge. I have at least twenty five years remaining (depending on the retirement age) and there are people who are younger and more senior than me. ie. They will still be very senior in BA after I retire!
Sadly, for anyone joining now, the retirement bulge has ended so there will be very little movement over the next few years. Looking further ahead, since the late 80's there has been a good spread of ages joining at relatively regular intervals, so the numbers of retirements will remain reasonably constant. There is unlikely to be another 'bulge'. This is before the 2006 legislation is taken into account.
Hope this helps. Once you've got some seniority, life improves immeasurably.