The biggest tip I can give you is to book everything yourself.
We have done this for the past 3 years, have had some amzing holidays, and although have been outwith the school holidays, and only 3 of us, have all come in at around 1k - last years' was all inc at a 5* in Tenerife, inc car hire.
We fly budget airline( as its the only one available from scotland), plus means we can pick our dates rather than having to do Tuesday to Tuesday or whatever. I then spend hours on tripadvisor looking at hotels, looking at reviews etc, narrow it down to 3 usually then spend a night getting the best possible price for hotel - websites like alpharooms, lowcostholidays etc are much cheaper than some of the bigger names, and are ATOL/ABTA protected.
This year, I actually went onto hotels own website, joined their e-club thing which was free, which meant that they would price match +10% - so got 6 nights at a 5* b&b in a suite for the 3 of us for £400. - Some websites were quoting over £800
Use a cashback site too - can get up to £100 back at times.