I've made it to Swanage FC by the skin of my teeth and have a problem that I am hoping the collective expertise here can shed some light on.
My buggy ran perfectly for the first 2hours (75 miles) from home but then started a misfire... 3 cylinders OK, don't know which, one not. This developed not a full blown stall. Breakdown service called and he removed, cleaned and replaced the plugs. Another 5 miles and the same thing again. And again.

Every time it gets hot, and under load, sputtering and death. I made it as far as Swanage and called into a local garage where a lovely guy explained that he thought it sounded like an HT lead issue. As it was Friday afternoon and he already had a full workshop, he lent me a a multimeter to test my existing leads , telling me that anything above 8ohms was bad. All leads were below 1.5 ohms

I set off from Swanage FC to test it out after tightening up the threaded ends of the HT lead as suggested and five miles in, same problem.

My (completely uneducated) gut feel is that it's a fuel problem but having Googled it and spoken to a few people it could be the coil, plugs, or any number of of other possibilities.

Where would you start, based on the fact that I'm miles from home, have almost no tools, potentially have a cruise tomorrow and the carnival on Sunday and need to get home, preferably not on the back of a recovery truck...

Run it for a little while. see if the coil gots really hot. If it does, try borrow one from another buggy, or someone's spare  See if that helps.

My first suspect would be the condenser, they can cause all kinds of madness when they fail, and sadly it's more likely to be faulty if it's a newish one rather than an old one.

You don't say if its points and condenser or electronic ignition?

Update:

I didn't get chance to test the temperature of the coil but replaced it anyway as that seemed to be the consensus.

However, a brand new coil supplied by Gav didn't solve the problem which almost everyone then diagnosed as being fuel-related (which was kind of the original thought).

A new filter along with some shiny new jubilee clips from Dom on some new fuel line kindly provided by Chad got me running well enough to take part in the cruise today (in the pouring rain!), should see me right to get through the actual carnival and hopefully all the way home to Bristol tomorrow.

I can't thank the guys here enough for the help, advice, parts and gentle pee-taking, you are all diamonds.

I have learned more about electrics, fuel system and other nuggets of maintenance hints and tips in the past 24 hours than I thought possible. I love this community.

That's the beauty of a camping weekend with the best pit crew you could ever find - Amazing how much you can learn