Oh, thank you all so much for your helpful suggestions. It seems such a mammoth task, sitting here thinking about it. I get the impression that the thing to do is be very organised before you go (plenty of pencils!) and then get there and just enjoy it.
I assume most of you must be like me and have ancesters dotted all over Cumberland? If so, what made you decide on a particular strand of your family (having taken account of Andrea's advice to search where there are good chances of success), or particular records office? Or, having seen so many comments on this thread and others, about how good the staff are in Carlisle, it doesn't seem a bad idea to just go there and ask them who I should search?
Jackie