Update : I finally received the credits I was due........ So was it worth all the hassle? In my case yes as I'm not yet a good enough player to win/earn any credits from Tournaments, and I cant afford the upgrades and balls I want otherwise.
Yes these offers ( casino type ) are a great way to save money - if you can deal with the frustration and anger these people cause you getting what's rightfully yours. I managed to get an email from Betfred in the end by constantly hounding them by email and phone, and that gave me irrefutable proof of my completing the offer terms exactly.
So my advice based on 2 hardwon offers with Supersonicads is :
Unless you're strapped for cash - like me.. DONT do it!!! stick to the surveys.
If you do spend money on one their offers, take Screenshots of EVERYTHING! and I mean everything - every step of your account setup and most importantly the page(s) showing the Bet placed and Time & Date etc. If you leave anything out they will look for it and use it as a delaying tactic. So you need 10 + screenshots to cover everything....
Finally as others have said, dont give up! if you have completed the offer correctly you are legally entitiled to your credits. I was definately going to take them to court had they not coughed up my credits this time, and they probably knew it.
Good Luck!