Given that you have £25K sitting in the account and you have been back in UK for 5 years it might be relevant to consider how much has been used out of the account and the actual interest eraned as opposed to the actual interest declared.
The side issue to this of course is that an Inspector with an open mind - yes there may be one or two left - might actually wonder if you should have been paying tax on the monies that went into the account and on hearing about the origin or "actual few hundred pounds" - this could be 200 to umpteen hundreds dare I say -might get interested.
You do not say what your line of work is or whether you are employed/director/self employed and therefore it is difficult to judge how prone to enquiry you would be by going forward cap in hand.Your comment that "I was resident in 2 countries at the same time and gave up trying to make things 100% correct at both ends" throws another potential problem into the equation.
Suffice it to say that I have found in my experience that a lot can be gained by "biting the bullit" right at the outset and making a full disclosure to HMRC to take advantage of the possible reductions in penalties for disclosure, cooperation and size & gravity.
Nearly forgot - if the ultimate tax liabilities are small enough so that the penalty that would be applied after all reductions was less than £250 you would only pay interest. Also if you happened to be non uk domiciled the problem might not be as big as first thought
You are probably best getting a specialist to look over all the papers - but he would need to have full details of your emplyment etc details and sight of all your banking accounts to start looking at the potential damage
regards
see my site if you are interested
http://www.wamstaxltd.com
or email me at
bill@wamstaxltd.com if you would rather not put too much financial info on interent.