This does seem to be a bit of a wind up when looked at more closely? £100 a week for DIY livery but you’re not allowed to go 2 days a week. Grass clippings put in the field - what do you mean by grass clippings? Are we talking cut grass as used on some yards or actual lawn mower clippings? You say you’ve 20 years experience but the young girl who sometimes comes to ‘help’ me would tell you she’s 10 years experience which when looked at more closely is a weekly group riding lesson. Your best option would be to use the £400 a month and find somewhere your horse can go over the winter where he’ll be safe and Msybe pick things up in the spring. If he’s recently broken he could be quite young and may benefit from some time off over winter. Equally if the first yard was a ‘nightmare’ it could be that he would benefit from some experience of a yard routine and equally you would benefit from having a buddy to help you settle in. Good luck whatever you decide.
I was expecting the OK to have messaged me for some suggestions by now.