drwex | The right tool for this job?

Once upon a time

rmd remarked that "the right tool for this job is your checkbook."

I am in the earliest stages of planning a possible family visit to the UK this summer. I have some constraints (duration, target locations, windows for travel) but a lot of flexibility. I want to optimize for price - the cheaper I can make the travel itself be the more I can spend on fun things to do while there.

I don't think any of the online sites I'm familiar with are optimized for this and I'm wondering if there's a site I don't know about or maybe it's time to employ a human travel agent. Although I am optimizing for price of travel my time also has value and I'd like not to spend a lot of hours poring over alternatives.

(Kayak seems to be the site closest to what I want but even that doesn't seem able to cope with "I want to travel around date X but if that's a bad season I can move to another month." Kayak lets me have a 2-3 date window in which I can run seemingly infinite numbers of searches on specific date combos.)