Wow MoS, I had not thought of that. Good call. I once grew mini sweetcorn and ordinary sweetcorn about 3 metres apart and ended up with rock hard inedible rubbish. What my wife called Brundle-corn, after the famous film "The Fly" with Jeff Goldblum. Should have thought my planting plans through.
UPDATE. After a bit of searching the old internet thingy, I've learned that you can safely grow Cucurbita maxima, with C. pepo and/or C. mixta and/or C. moschata. Which explains how my courgette (zucchini for our American chums) and butternut squash left each other alone as they are pepo and moschata.
Another handy tip was to plant each one 1/2 mile apart. Yeah right. The people who can do that are not called gardeners, they are called farmers.
So, as I cannot tell which is which until there's some fruit on them, I'm going to risk it. I've got
Cucurbita pepo … Acorn, Small Sugar Pumpkin, Spaghetti, Table King, Potimarron
Cucurbita maxima … Blue Hubbard, Jarrahdale pumpkin or Australian pumpkin, Rouge Vif d’Etampes
Cucurbita moschata … Butternut, Musquee de Provence or the Fairytale pumpkin.