If this debt is from 2009 then it is likely that any damage that could be done has already been started and is already affecting you right now.
It is likely that if this debt has not been paid from 2009 you will have incured a Default against your name. This is a marker against your credit file which will state that you are a poor credit risk and have failed to repay the debts you have taken on. This marker will be a shining beacon to all other credit providers from mobile phones to personal loans and credit cards up to mortgages and other finance. The default will warn lenders that you have previously failed to keep up the agreed repayments on your credit facility and this alone could be enough for any provider to refuse you credit. You stand a good chance of an automatic decline for a mortgage if you have a default on your file.
You cannot remove these markers from your credit file, it is the penalty for failing the credit agreement you took out. Paying the debt will only mark them as "satisfied" but the default marker will still remain on your credit file for 6 years from the date it was placed so if it was placed in 2009 then you will likely have the default showing on your credit profile for all potential credit lenders to see until 2015. Unless placed incorrectly (which you say it most likely hasnt been) it is impossible to have it removed.
If 3 sell the debt onto another company the first thing the other company will do is add administration charges which will rack up what you owe in total. If it is £230 now it could well end up at £350 or £400. These guys will chase you and hound you with letters and telephone calls to try and get the money back. If you refuse to repay the debt still then they can take further action such as bailiffs and county court action. You will find it very hard to turn away from this debt and quite frankly if you owe it in the first place then you can hardly complain if they want it back.
You will not be made bankrupt over the debt, the total has to be more than £750 I think for this to happen and you are not even close to this but this does not mean that the methods used to gain the money back will be any less damaging to you and failure to pay the debt will almost certainly ruin any chance you may have for a mortgage in the bext 6 years and quite likely you will struggle to get a personal loan, credit card, car finance and potentially even an overdraft with your own bank.
If you owe the debt, buckle up and just pay it. if you don't have the £230 to spare (who does) then call 3 and talk to them and you should be able to arrange a payment plan with them and this will save it going to a debt recovery company who will just add to the bill. As soon as you pick up the phone and communicate with them then this whole debt will become alot easier to deal with.
Good Luck.