If you're doing high mileage then I'd recommending buying outright, as most lease deals will have strict mileage limits that might not suit your working life. Personally, I'd search for a pre-reg van as these can offer big savings that could cover the £6000 you'll spend on the conversion. Pre-reg vans are effectively surplus stock, sold cheaply as “ex demo” or “delivery mileage” vehicles with savings of up to 30 per cent.

The Ford Transit Custom is one of the best medium size vans on the market: vans.honestjohn.co.uk/van-reviews/ford/transit-cus.../

But I'd also consider the excellent Toyota Proace as this is backed by a five-year 100,000 mile warranty: vans.honestjohn.co.uk/van-reviews/toyota/proace-20.../