Thomas Cook fly from Newcastle every Friday.
I dont know what the prices are like for September but todays flight was £88 return and last Fridays £68.
My friend has an apartment near Sunny Beach and last September they had poor weather so decided to go in June instead.

Thanks for the info Jay Trip, but we need to check into our apartment on the Monday so a Friday flight is a no go. Sorry. Thankyou for trying.

Balkan holidays and Thomas Cook fly to and from humberside to bourgas every Sunday departing Humberside at 19:50 and arriving at humberside 18:50. I'm going a week on Sunday and they fly them times until 2nd October.
humbersideairport.com/huyweb.nsf/Content/bourgas#timetablesNew

Hope this helps

You could look at Wizz Air from Luton, i believe they fly out every day until late Sept, then return 3 days of the week towards Oct. Last time i looked the prices were reasonable also.

balkan fly newcastle mondays flight time 18.20pm

manchester might be your best bet balkan fly from there wed fri sun mon xx

Agree Manchester is probably your best bet. Balkan, Thomson, Thomascook and Monarch all fly from Manchester on Monday's and all have flights for the 12th Sept. If your able to hold out Balkan usually start reducing their flights about 6 weeks before departure and the nearer the departure date it gets the cheaper they are, with 6 of you i know this may be risky as flights could sell out.