Britannia now have 5 B737-800s, 2 based in the UK and 3 in Scandinavia, plus a UK-based A320 operated by TransAer.
In my opinion Air 2000 and Virgin Sun are both better than Britannia. See these Trip Reports if you want to know why;
The Charter airlines do generally provide very good service, better than many US scheduled airlines, although legroom is tight you can upgrade on longhaul flights (for around £100-150 RTN), and on many Air 2000 shorthaul flights from next summer (for around £30-50 RTN) These supplements still make the flights a lot cheaper than scheduled services, with more legroom and better service!
If you pick your airlines and flight times carefully you should also manage to get away on time, or reasonably so, I'm not going to complain about a 20 minute delay!
Apart from the higher scheduled fares, on most holiday routes in Europe there is no direct scheduled service anyway, leaving you little option about choice of airline.