Shortstripper - haven't seen a response to your query, but it seems to me that iff Goodwood has an A/G service, it is you who are in charge, and you can, theoretically, do what you want. They might not invite you back if you do something silly, but taking off half way down a runway in a STOL aircraft wouldn't really constitute that.
If it is AFIS, they have the power to give instructions to ground movements (I think), but if you say you are lining up for take-off and then take off, you can do it, because they have no authority to grant you approval for take-off or refuse it.
Why not have a word with the aerodrome manager? They are probably concerned about noise, and you might be able to discuss the whole thing and reach a common sense answer (although in my experience, common sense is not common at airports!)