Marina di Chioggia
Have compared my long storing pumpkin with my seed packets and decided that it was this one.
Marina di Chioggia. I got the seeds at Wisley but Franci seeds are available in lots of places.
Googling these found this info on the seed (My packet is in Italian so not much info on there)
"Very old, rustic pumpkin from near Venice. Thick, knobbly skin and sweet yellow/orange flesh. Rich in Vitamin A which helps keep eyes and skin healthy. Also contains mineral salts (Calcium & Phosphorous). @9. Sow Mar-end Jun and harvest till the end of November."
Another site has a picture http://www.flickr.com/photos/kthread/4103587009/
And another describes it here as very long storing http://www.gardenharvestsupply.com/product/marina-de-chioggia-garden-squash-squash-vegetablesTheir picture shows a more warty pumpkin than mine was.