Chinchilla
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Exmoor might be a bit small. Personally I would go for a New Forest - there are sales soon I think. They make great alrounders and are lighter built but strong and quick. Hence why a lot go show jumping.
Get an NF! They are brill! Dirt cheap at sales* as well but fun little things if you treat them right; can do absolutely anything, and do it a way that makes you smile every time.
EKW yes the sales happen in the autumn generally after the foals are weaned. The dates for this year can be found here: http://www.nfls.org.uk/sales.htm
* There's a minimum bid of 21 gns at Bealieau now. Think that's about £22.05 but can't remember what a guinea is worth.