I use Super Clean, which is an automotive de-greaser. It used to be made by Castrol, apparently, but it think production was spun off.
I use glass jars of various sizes, depending on the size of the piece. I used to use oven cleaner, but the major drawback to oven cleaner is that you can only use a batch once. Super Clean can be re-used over and over.
I first tried it, after one of the guys at the Agape modeling forum showed that he used it to remove the chrome from Tamiya's chromed P-51 kit. I wanted to strip the chrome from the chromed parts in the Monogram Red Baron hot rod kit. I used an old baking dish, big enough to fit the sprues, and poured in the SC. It dissolved the chrome from the parts in under two minutes, leaving them literally squeaky-clean, since there was nothing between my fingers and the bare styrene.
I next tested using it to strip paint from some metal figures, and found that the paint started dissolving after a couple of minutes. The longer the piece soaks, of course, the more the paint will dissolve into the solution. But I usually give it five to ten minutes, and then I find I can scrub the softened paint away gently with an old toothbrush.
I use it now, too, to clean styrene and resin parts of any mold-release agents, before assembling a kit and priming it.
And since I can use a batch over and over, and a gallon jug runs about eight bucks at WalMart, it's a much more frugal choice, than cans of Easy-Off.
SC can also be used around the house for cleaning away grease, so that makes it even more attractive as a tool.
I can see only two possible snags in this particular case: I don't know if it's available in the UK--it is available in Canada--and I have never tried to strip the paint off a Del Prado figure. But I can't see why it wouldn't work in that case, either.
Hope that helps, prosit!
Brad
