The best thing to do (done it myself) is:
1. Decide where you want to go, and preferred Hotels.
2. Check it out on Tripadvisor.co.uk
3. Go to travel agent, get a quote.
4. Go to another travel agent. Ask them to beat the quote.
5. And so on...
6. Compare the best price you get with online sites/Teletext.
I've doen this several times and got several hundred pounds off.