Indeed you can consume anything unless of course it's a substance banned by UK Athletics or whoever the governing body is...
Also check the rules of the race you're entering, I know in my local half last it, it was allegedly against the rules to have somebody (other than race marshals) hand you food/drink?! I think you'd be pretty unlucky to get pulled up on this one though!!
I took Powerbar Powergels with me to the Frankfurt Marathon and put them either in the back pocket of my shorts or under the sweatbands I was was wearing. That way, I didn't have to worry about anyone handing them to me. Some of the other runs were wearing those runners belts for the same reason.