Andrew Gould is excellent + one of his, Habanero, is a PRE. Based in Ebbisham, Surrey but does teach at other yards in the south east. Check out his website for dates/locations.
In Kent, I'd highly recommend Bertil Voss. Very patient, teaches to Grand Prix, explains what, why and how, in a way that means you can teach yourself between lessons. He's been a Godsend to us.
Debbie Moore is very good. She trains one of our former livery clients and would come up when the client was on holiday to feed carrots and pamper. Lovely lady.
What about finding someone at Oldencraig? they have Iberians there and I have had one lesson there. I was worked so hard that when I got back in my car, I actually steamed up my windows. That wasn't even in the depths of winter that was on a spring day!.