Hey Alan,
Last year I was in the same position as you, I didn't need another car, but a particular 544 was taunting me. It first appeared on eBay but we didn't have the money for it, then it appeared again - for sale by a friend of mine, and I knew it was sending me signals! So I bought it just before Christmas. On a whim
Mine's nowhere near as pretty as that white one - it's got a few rust holes in the door bottoms and in the boot floor, but it's also covered in a sort of wonderful patina - and because a respray would be a lot of time and money, it's staying patina'd for some time
Mine was a bit of a barn find. It's been off the road for about 20 years, and recommissioning it has cost me a pretty penny. If I were to bring it up to the standard of the white car, it'd cost me close to £10k, so if you see a really nice solid one for £10-11k, it's probably about right.
They're rare cars as it is, but that white one is one of the earlier 544s, which make it even rarer. As others have said it'll be a 6v car with a B16 - not the slowest car in the world, but not quite as pokey as the B18. I would take Kassie up on his offer and go look at one of his - he usually has at least one for sale!
PVs are real head turners, great fun to drive and really quite lovely - plus if well looked after they will hold their value.