I have no idea about the availability in the UK, but here in the USA at least the prices are dropping by the month. So it's definitely worth taking a look... any fish clubs or do your LFSs work with any reputable importers?
But if there tank bred how can they still be called wild? How many generations do they have to be before they are counted as not wild? Or is the term 'wild' just used as a common name for that type of betta?
The issue isn't really whether they're F1 or F10- but whether or not they've been crossed with domesticated bettas resulting in the super-aggressive domesticated genes. "True" wild Betta splendens are not nearly as aggressive as domesticated Betta splendens as they have not endured generation upon generation of breeding for sport fighting. Most domesticated bettas in the hobby today still come from those original Asian fighting lines... and the fighting "sport" unfortunately is still going strong in Asia.