There are shows in Leighton buzzard run by there riding club all through the summer they have in hand classes, if you Google the website should come up I think they start around April.
depending on where you are Northants Riders Club and Rushden and District Riding Club may be options, their early shows tend to be quite quiet and both clubs are very helpful and welcoming
www.greyfernpark.co.uk does monthly showing shows in Peterborough. I would also take a look at keysoe and college of west Anglia websites they often have showing think brook farm in Essex might too.