They're grown as annuals but some will survive a moderate winter and come up every year.

Sometimes they survive but I find they go woody and leggy the following season.

I find the same as Hywel.

I find that they also self seed, and pop up in many places the next year. They do seem to go for 2 summers.

We are talking here of the ones sold for bedding, there are perennial Antirrhinum, like A. molle and A. pulverentulum and various others too.

I didnt think the perennials were known as snap dragon I thought that was applied to the annuals?

I have one of two supposedly annual ones that have come up for several years, and also self seeded.

Yes I have some pollen free antirrhuinums (free sample of seed!) some of which have self set and some have survived from last year. They do get woody but I get around this by plunging them even deeper into the soil and they bush up a treat. Posted some pics on my blogs :-)