A copy of a post 1858 will can be bought from The Probate Registry in York, using the form signposted by Mo above. They take about 4 weeks to arrive (well, mine did earlier in the summer). www.theprobateservice.gov.uk gives more info.
When you say "the date is wrong", don't forget the will date is not based on the death date but rather on the date when the family got round to applying for probate. It can even be years after the death, but was more usually a couple of months in 19th century.