I'm not over convinced that any of the small (or even smallish) safes that are widely available are too secure unless you pay a fair bit of money for one. The main thing is that they slow down an opportunist thief who has already got into the van and he would have to make a bit of noise to get the job done. That said, if they manage to steal the van, I doubt the safe exists that they wouldn't be able to get into eventually or, with the right tools, very quickly indeed. As for myself, I've got a small Yale combination safe that also works with a physical key (3 supplied) if the keypad batteries run out of juice and IIRC it was around £110. It's not in the seat base but I don't see any reason why it wouldn't fit in there (but bear in mind that you probably wouldn't be able to fix it to the bottom of the seat base because of the swivel plate and that's why mine is fixed elsewhere). There are loads of different ones on the market from £25 odd and you just need to google 'small safe' or 'compact safe' - they're one of those things where the more you spend the more secure they get. As I indicate above, it's all about slowing them downor putting them off rather than finding something that's thiefproof.