If you can look at parish records, you can often find extra information, that isn't on the IGI, which enables you to work out who's who. For this you need to visit the Heritage Library but they records are due to go on-line later in the year.

Looking for memorial inscriptions (from headstones) has been invaluable to me in because they usually state family relationships. You can look in the library, order books for different parishes from the Fam. Hisy Soc or ask Donna... as she is so kind! Hope you don't mind my mentioning you, Donna!

Wills are excellent too for the same reason, often giving married names of daughters and mentioning grandchildren and nephews etc. Many have been summarised by Frances, many are on the Lawsons Micro site or else you can trawl through the microfilms at the library, but I believe the intention is for these to go on-line at some point.
Good luck!
Jo