Hi Leanne,
Whereabouts in Aberdeenshire are you? I'm towards Banchory and possibly looking for a 5* home for my retired Cob mare. Only issue is she would have to come with her own little furball companion - a 9yr old (ish) Shetland mare. They're both tough critters and live out all year unrugged, just some shelter and a bit of pampering now and again.
Other than that have you tried SSPCA at Drumoak or World Horse Welfare in Aboyne? You probably have so apologies if that's a 'suck eggs' comment.
Dear moderator - above comments ref rescue defunct as someone else has now suggested them. If you get around to checking this post then please just include the first part.