Your post was spot on.
From the B757 fleet, some Senior F/O's (mainly ex-DHL) are indeed leaving to go to BA,EK, EY & QR but these are all under 40 years of age & you'll always get that as some people, quite right,ly want to progress to 'National' carriers.
I haven't heard of any going to VAA... yet.
Some are also going to TCX & TOM because these offer Southern UK bases, in-place Scheduling (Rostering) Agreements, Short/Long Haul mix, fairer T&C's in terms of pension contributions, Day Off payments, basic salary & FDA & a major player which is discounted Staff Travel.
I don't know if it's as dire as 6 FO's left at MAN but the remaining guys are all seasoned pro's, each with well over 10 years B757/767 ETOPS & global route experience, generally 40+ in age & are all in the next tranche of Command slots on the B757. More Pilot Apprentices are being trained for the B757, a liberal sprinkling of returnees from the Gulf' & those moving on to 'Bigger Things' coming from turboprop commands being trained up over the winter will ensure that the numbers are back up to normal levels as the season starts. In addition to a smattering of transfers from the B737 fleet.
The B757 Captains are pretty much a settled bunch, with annual totals for Line Captains rarely getting above 400 hours, Trainers do have it tougher with TRI/TRE's shuttling up & down the M62.
The pay is on time, albeit at the lower end of the salary rankings for similar operators. Company is doing well, not over exposed in the Mediterranean trouble spots, no 'Deep' night flights that blights most Charter/IT rosters, they own most of their aircraft outright, they're spending squillions of quids on cockpit & avionics upgrades for the B757 investing in them to keep them for the next 7-10 years & brand new B73NG's to replace the older B733's. They're increasing in size at a cautious rate but the rise in share price glows of cautious, shrewd management. When I joined it was 75p, now its around 525p in 5 years. Forward bookings are way ahead of already ambitious predictions for S2016, it's looking rosy.
The management just needs to give internal upgrades to it's most experienced SFO's, provide competitive T&C's more in-line with its competitors, introduce a Staff Travel scheme & a Rostering Agreement IF it wants to attract & retain its experienced crews.
Because all in all its not a bad job, with fun crews & simple flying.