On the way to the little car show I run, my Moggie died.

So--
It starts and idles fine, but when I press on the accelerator, it dies, but doesn't totally cut out, just back to idle.
1275 A Series, single HIF 44 SU carb.
I really haven't done anything apart from having it towed back home, and I'm not much of a mechanic, but I don't know where to start.
Thanks in advance,
Dave