Hi. Oliver is now 2 1/2 and we have quite a few friends with similar aged babies who are all speaking really well. His hearing is fine and he understands what we say but apart from "elo" for hello "bye" "mama" (which he calls me and his mum, although dada was his first words he never says it now) and then a few sounds like "what's that". He even used to say "tar" as thank you but doesn't anymore. We also have a 5 month baby girl Heidi and he has been fine with her and he has been at nursery around other kids since he was nine months. Me and my partner are now very worried about his behaviour and lack of speech. He loves arranging things and watching Disney DVD's and diving on me for fun but as soon as I try him with a book he either quickly turns the pages or shouts "no". Any advice would be appreciated thanks

There are countless very bright and accomplished people who didn't talk on the usual schedule, some waiting until as late as 5.
On the other hand there could be a cause for concern, and you just don't know until you have him tested by a speech pathologist. That person can look for physical problems like the palate or other mouth development that is hampering the ability to speak, as well as test reactions and motions and what he will/can say.
Even testing isn't always correct with a diagnosis, but you should have it done.

People diagnose kids now and go nuts over speech when 10% of boys talk late. Smarter boys seem to exhibit this profile commonly. The problem is AGE. You can't read to all 2 year old boys. You might want to try to find a high interest book with flaps, most boys can't resist that, lift the flap. Meet him where he is at and have fun. Repeat words often in a meaningful context. Good luck! Enjoy your son!!