How much are you paying for trailer rental these days? I’ve just got back into trailer rental and some customers seem to think the going rate for a tri-axle curtain is £70 - £75 per week inc of maintenance and tyres! If finance on a trailer is £55 - 60 p.w. can you tyre and service it for £15? I know i can’t! 
Hill hire in Bradistan charge £80 fully inc. for a 4.2 taut. the advantage over the other shysters is that they don’t want a month up front.
Very fair to deal with and not overly picky on return. Hireco on the other hand, opened my account, talked to a chap at Wakefield and thought sod it. Still use HH.
Regards 
One of my customers had a load of (admittedly far from new) 13.6m / 4.2m curtainsiders from Bell over at Nelson and they were only paying £75 which I know for a fact included servicing, not sure about tyres. Not sure what they’re paying for the new ones though.
Paul