Collins field guides are all very good.
My 'Complete British Insects' by Michael Chinery (collins) is very good. You'd have to have some biological guide book from the Natural History Museum to get every species or sub species though. I think the best thing to do is learn the basic insect/spiders off by heart then,as you are a photographer, get some good close up shots-helps sometimes to get a bit of the plant the insect is on, then post it on WAB.
There are some true experts on here,Imaginos/Henrya/Fourwings and many more, who really know their stuff and 99.99% of the time can ID straight away.
I suppose you could always take that lot with you-but I doubt if they'd fit in your back pack!!
I've just had a good idea.... The WAB Field Guides to the Wildlife of Britain, Has a good ring to it!!!
John can id birds 5 miles away with his eyes closed, Fungijohn, the fun guy, any toadstool at 40 paces, loads of brill photographers (yourself included) for advice, Boddie the camping expert, Gill/nicole the reserves experts...oh the list goes on... all members of WAB actually.
Right, now I've 'big-up'd' WAB, post some pictures and watch what happens.
Good luck getting your guide. ww