have you tried http://www.skyscanner.net/

Go on all the airlines websites such as

http://www.Thomsonfly.com
http://www.flymonarch.com/
http://www.Thomascook.co.uk
http://www.firstchoice.co.uk

Try Thomson for the accommodation as they do some silly rates, I just paid £89 for three nights 4 star accommodation in Tenerife
A great place to start is also the gatwick airport website, this will give you an overview of the flight times, and see which operator has the best times and days to suit you.

I have copy and pasted the information so if it looks a bit hard to read try following this link instead
http://www.gatwickairport.com/portal/page/LGW%5EFlight+Information%5EFlight+Timetables%5ECharter+Flight+Timetable/

Looks like Monarch dont go,
First choice go Friday and sunday
Thomson Tuesday and Saturday
Mytravel(Thomas cook) Sunday

EDIT: Sorry, but the information quoted was copyright protected and had to be removed
David HT Mod