It could have gone in that time, who knows how well it was treated and even if it really was changed or if the mileage is genuine. It could have been a caravan towing, clutch slipping owner before.
It might be worth a google on adjustment but I don't think there is any as this would be a centre push hydraulic clutch. The fluid may need a change and bleed but it does sound very like a worn out clutch to me.

I would get some independent quotes or do it yourself.