The costs of a full loan (Uk)?

There isn't a set price for full loan - it's all dependent on where the horse is kept and such. Basically, the best way to explain it is that the owner of the horse only pays for insurance. You pay for everything else e.g. farrier, livery, anything else you decide to buy for it and some vets fees. If the horse had to go in for a major operation, the owner would at least be involved in the fees of this. And I'm pretty sure you only need riders insurance.