I used to live in Wilts but can't now remember who'd be good or bad - throw me some names and I'll tell you if I know / remember any of them? I wasn't farming at the time, but was WWOOFing and was always looking wistfully at smallholdings and land to buy...
Re: SFP, I think that broadly land had to have been registered by whoever was farming it in 2002 or whenever it was the scheme started. Since then entitlements have been bought and sold, but the payments can only be claimed by whoever is farming that land on a certain day in the year - I think it's May 15th. And you have to state that you expect to still be farming that land by some other date, I think it's in October. I think landowners can claim for the land they rent out, as they are causing it to be farmed, and I am sure farmers can claim for the land they farm on a tenancy or grazing license as we have one field on a tenancy and some on an 11/12 (one month vacant per annum) grazing agreement, and get SFP for all of them. We have summer grazing on one other field and do not claim SFP on that one, although I think we probably would be eligible with the landowner's approval.
I suspect that the landowner's agreement would be required for claiming SFP on ground you do not own.
When the current SFP scheme was introduced, many retiring farmers bought 'naked acres', small pieces of ground on which they could hang their historical entitlements. But the historical component of the payment is now zero, so all payments relate to acreage, type of ground and type of use.
I'm not very certain of all this as SFP is so complex we pay someone to do ours; I maybe could work it out myself but am pretty sure it would shorten my life every time I had to get into it; the HLS scheme certainly does. When I'm dealing with an HLS query, BH runs for the hills until he thinks I'll have it finished.
I don't know whether any of that helped at all, or just made it all more obtuse!