Charlie - just sent you a couple of PMs with some route tips gathered from others a few years ago which came in useful for me.

As a fellow soft southerner, my only advice would be to set off nice and steady and try and save a bit for the ascent of Dale Head, and even more importantly, the descent back down through the quarry - it's is very steep and very hard when tired!! It's all to easy to get carried away in the cavalry charge along the lane at the start. Set out with the aim of enjoying it and you will probably do a better time than if you try to race it!

Last time I did it my kids and Mrs managed to entertain themselves by heading up to Honister Pass. It's a good place for them to come and see you as they will be able to get back to Rosthwaite in time (unless you are super quick!). Pretty miserable for them if its pelting down mind, in which case the Keswick pencil museum might be the thing
Oh, and one last tip - the cheese sarny and cup of tea in the Rosthwaite Institute after the race will be the best thing you have ever eaten