Now that almost all flights can be booked online, the price is probably the same wherever you book from. (i.e. you, or your travel agent, will probably connect into the same computerised system, wherever you are).
Even so, if you book early and travel mid-week there are still some reasonably cheap fares to be found. For instance, Ryanair will fly you to Malta (from Luton), in the peak summer holiday period for �49.99 outbound (on 15th August) and �69.99 back (a fortnight later, on 29th August). With taxes and charges, that comes to �157.42. (Those are just some specimen fares I found quickly. There may be cheaper fares available if you try other dates).
Even when you only get one week break (so mid-week to mid-week booking isn't possible), there are still some reasonable fares if you book well in advance. For instance at October half-term (assuming that you have the same dates as we do in Suffolk), you can travel out on Sunday 21st for �29.99 and return on the 25th for �69.99. With taxes and charges, that comes to �137.42.
I was having to pay those sort of fares to Malta, during the school holidays, 25 years ago (when my teacher's salary was considerably less than you'll be getting now), so they certainly look like bargains to me ;-)
Chris