I had the same happen to me when I did the sub over chelt. My £100 freebet won and I whacked in a withdrawal for some of it but nothing happened for a few days. Got in touch and the CS guy mentioned abuse and said they had a spreadsheet of all freebet winners that they were working through, but as he had spoken to me he said I wouldn't have a prob and he would call me back with an update. Was happy when the withdrawal hit MBs before the CS guy called back.
McBookie updated their site (here) and an email went out (can't say it was directed to all accounts of course) offering customers the free £10: "Due to bonus abuse we have been forced to withdraw our Cheltenham Free Bet Offer to Tartan Club members. However, as a customer of McBookie who participates in the offers on a regular basis we would like to offer you a free £10 matching bet as an apology for pulling the offer."
Cheers. Probably didn't get anything as this was the first (and obviously last) time I took part in an offer from them.
Withdrawal request made on 18th March
Request FINALLY processed on 5th April
Payment received 6th April
Looks like they're not withholding payments - just SUPER slow at dealing with a backlog. Not one piece of communication. Very poor. Bonus King my arse. It's not like there isn't LOADS of other competition in the industry... I'll be betting elsewhere!!!