Can you get a deault removed early?

Ok, Ive turned my bebt around big style in the last couple of months simply by reading Martins book and with the help and inspiration of this site. I have had a few searches lately, but have changed every aspect of my finances except utility bills, but there are reasons for this just now. I am not looking to start any new accounts til around the end of the year.

My longest 0% offer ends in mid Novemeber and I hope to have cleared off the current 3k balance by this time, but being realistic and about to undertake home improvements such as a new fitted kitchen and installtion of gas central heating (all money in my bank and stuff in the middle of getting organised), but I am aware I might need more than Ive budgeted for unexpected finds when doing the work. So, in that case the 3k on my One card might not be fully paid off, so would want to switch to another 0% card before then if I needed to.

Thing is, I thought the searches would 'expire' before then and not be shown, but there seems to be conflicing advice on this.

I got a default in May 2000 from Bank of Scotland on an account I wish they never offered me. It was a revolving credit account where I got a switch card and a cheque book and was charged an obscene amount of interest. The terms werent explained to me at all, but I can only blame myself for not reading things carefully. That is not the issue. I was going to write to them to ask if there would be any possibility of removing this default early, possibly even May this year - one year early. I still bank with them, have my mortgage with halifax, have their 0% credit card now and a loan. Do you think this would help or hinder me? Just increased my loan with them partly to get the works done on the house, and they offered me the same account again that got me the default! Even when I called to say I did not want it they said just ignore the forms, but since then Ive had a few letters saying Oh, we havent got your agreement back from you yet LOL.

Anyone done this? Are there other things to consider here or best ways to go about it? Without being big-headed, the letters I write do seem to get results, but with this I only really have one shot. I have nothing to lose by asking me, but apart from this default and missed payments with barclaycard in 2001, my credit report is otherwise in pretty good shape, and will be even better once the latest searches are wiped, and I have lived at this address longer. I assume it is technically possible to do it, whether they agree or not?

Cheers
JW