Comparing values with those of today is not straightforward because they can be calculated using many different measures, and things which might be expensive now could be cheap then and vice versa. It has been suggested that the most accurate measure would be a comparison of retail price indices.
Current data is only available till 2008. In 2008, £800 0s 0d from 1845 was worth:
£64,600.00 using the retail price index
£85,000.00 using the GDP deflator
£618,000.00 using the average earnings
£909,000.00 using the per capita GDP
£2,020,000.00 using the share of GDP http://www.measuringworth.com/ukcompare/