daveG. Try emailing Rachael.booth@tui.com
She sends out a weekly list of TUI flight availability from Dalaman to UK airports with dates and prices. They all include 20Kg luggage.
There wasn't anything to LBA in this weeks list, other than one leaving today, at £129. These are just for September, but if you can be a bit flexible with your dates it might be worth a try.
Nearest one to your requirements is Doncaster/Sheffield on 24/9 at £197.