Matthew I may be wrong, but a long while ago before we were vat registered, we looked into leasing and we told that we couldn't business lease unless we were! This may have changed, we may have been told a load of old rubbish, but hey, we went down a different road and now have 4 vans on the road and not a brand new one amongst them!
Is your x reg playing you up? we have a M reg 150,000 plus on the clock and still going strong. Serviced nore regularly than the newer ones though! understand what you say about reliabilty, but you can get problems with brand new vehicles too!
If you could lease, every leasor has a different deal going, so sorry can't even guess on the cost of buying