My under the counter integrated freezer has given up the ghost, I've no idea how old it is as it was in the house when we bought it, if I buy a new one, will the cupboard door fit on it, are they all universal?
Not the actual size of the freezer boxy, it's more the brackets on the door front, if you get what I mean, I don't know if I'm explaining myself properly.
You should be supplied with a template along with the new freezer and it's fittings. Take the old fittings off the door and fit the new ones per the template. You just need to get a new freezer that is a similar size to the old one so the old door will cover the freezer door. Take a look at some online suppliers. Assuming that you're happy to have a similar one you could search on the name of that one and see if it comes up, or if a newer replacement model is suggested.