I now seem to be sorted for ponies. Jonny passed the vet with flying colours (he has itchy back legs from mites, and he needs to see a farrier soon), and I'm paying a deposit tomorrow and probably collecting him a week on Monday. He's pretty much your classic heavyweight cob, and has been very well-behaved each time we've been to see him.
Picture below, behind a cut tag. He's a bit muddy, because he's been living out and the weather has not been all that dry recently.