Thanks for all the advice guys.

Wes, the 7x5 looks good and is obviously not taking the pics by being too small. I think I'm leaning towards getting one that size. The photo helps a lot!

Grey haired bloke, im definitely going to try and make sure the characters are all the legal size. If it won't fit on a 7x5 then I might have to rethink my options.

Does anyone know any places within Wiltshire that do special sized plates, or would I be best off ordering online?