Sigma EF 500 DG super with Canon 50D

[Barrysprout]

After upgrading my camera last week from 450D to the 50D I have been having problems with my flash. The problem is that it does not seem to know where to zoom to and hunts back and forth. Tried it again with the 450D and it works fine. Rather miffed because according to the Sigma website they are compatible.
After contacting Sigma they suggest a firmware upgrade. But they either want £5 along with my original receipt or £35 without it. Funnily enough after the original guarantee expired I didn't see a need to keep the receipt.
Is there any other way or place to get a firmware upgrade?

 

[Flash In The Pan]

You shouldn't need the receipt, just proof of purchase -credit card bill showing the transaction, something like that...

 

[Barrysprout]

Thanks flash, I really don't have anything though. Not even sure how I paid for it. I will pay the £35 as it's a good flash. Just annoying to have to do so when it's listed as compatible. And more annoying to note I could have saved myself £30.
My other option is to sell the sigma and put the money towards a second hand canon flash.