warmest places short flights would be the canary islands although you may get the bad day (we have been lucky) it is usualy the odd day and not like the uk
we usualy go on a package ... for flights you could try
lastminut,skyscanner,cheapflights or there are several scrapers put "cheap flights" into your google
we just got cheap flights with ba http://www.ba.com for 5 nights in augaust we find it works out a lot cheaper to book fligths and hotel seperate for a short stay as the package deals mostly cater for 1 week and 2 week stays.