Not sure how far you are willing to travel but I can recommend Ian at the Working Dog Company in Ickleford, near Hitchin. Probably about a 40 min drive from Leighton Buzzard? I've been to him with Juno and he is very good - and very calm and patient - we got a lot out of it. He owns and works cockers and labs and does one to one and group lessons.
You'll find the website on Google and they also have a Facebook page.