Bouldering and rock climbing in India is still in initial stages. Hence it will be difficult for one to find any rental shops (probably none) in Hampi. And Lonely planet says it is better to bring a decent bouldering mat and plenty of gear from home. And also Hampi being a UNESCO heritage center, bolting is limited to places.
And with respect to guide book, I found one written by Rohit Chauhan. I can't comment on the book as I don't have one. As per the book details, author is currently residing in Spain. Hence getting the book shipped to your UK should be easy.
On a similar note, try to plan your visit to Hampi between October/November and January (winter in India). Rock climbing in summer is a task next to impossible due to the heat. It would be better if you are in a group (4-5) instead of just one or two going for rock climbing.
Update: A friend replied to my tweet saying, one can in fact rent the equipment in cafes in Hampi. And one of his friend has a guidebook with list of all rocks in Hampi. Will update once I get book information.
Update 2: Detals in Gapp's answer :)