David - I do subscribe to FindMyPast but I don't find the Lincolnshire records any easier to search on there. For instance I chose St Botolph's Boston, and got 61 pages, with 50 images per page. So even if you know an approximate year, you first have to make a guess as to which page it would be on and then which set of records. Also despite it showing that the baptismal records are supposed to be from 1622-1911, the first line on the first page starts at 1833.
Penny - thanks for your reply. I can't remember which parishes and dates I was searching for, I have many ancestors from Lincolnshire and frequently do searches to find their baptism and or marriage dates. The records I've been looking for are mainly 17th and 18th century so data protection is not a problem. Most of them do seem to exist but suggest they are available in the reading room in Lincs Archives, but as I live in Hampshire that's not very useful for me. Perhaps, as you say, they are too fragile to digitalize.
Lizzie