You can take Gold DofE up until the age of (think it's) 21 (but may be 25) - look on the DofE website for the criteria needed for it. I know that it's offered to AIs in the ACF and other Cadet Forces, so it may be worth asking your OC.
All awards need to be completed by 25, not 21. No idea about whether you can do the awards through the OTC, but if not, many universities have their own DofE society. Your local area will very probabky have an Open Award centre as well.
Chocolate Frog - I believe it's officially called the "brap brap brap" now, in order to be fully street.
21? 25? My lad just got back from finishing his silver DOE today on his 16th birthday. Not that thats supper special just wanted to break the ice. The best bit was this evening when he said "Dad is my Bergen heavier than a civvie ruck sack?" of course it is son its a SAS Bergen and your Uncle Andy lined it with lead special for you going up Snowdon
I just wandering though because I would be going to the East Midlands OTC, and it's the only one without a website so I imagine the funding is quite low, just hoping they will have a DofE society at Leicester Uni, should do though.
I might be wrong, but you could try for an Army funded gap year. I think you do have to go through selection and so on, but I know some people who climbed Kilimanjaro (probably spelt wrongly) and didn't pay a penny.
If thats your kind of thing, then I suggest you look into it.