I am almost to the point of being obsessive-compulsive when it comes to tax returns, but if I were in your shoes.....I would not go back to point zero to 'fess up. In all likelihood, unless other reportable/taxable income was significant, you probably still would have owed no US tax.
A few years back, I did my annual SEP-IRA contribution, as always, near the dreaded April 15 deadline. A couple of years after that, I was looking through some paperwork and noticed that the bank person put the wrong tax year on the form. Did I go back to correct that (which would have affected 2 returns)? Nope, hands up, I did not, as my fuzzy math re-check told me that the overall tax due would have been the same (actually a bit less, as my larger SEP contribution came in a year when I was in a higher tax bracket, and I was still way under the maximum contribution as self-employed) . Don't stir that hornets nest if you don't need to.
FBARs - well, yes, if you needed to file, you need to catch up. After all, you may be a mega-rich drug overlord and the feds want to know where you keep your bazillions.
Do you need a consultant? Probably not, and the cost of using one is likely far more than the IRS might have collected if you had reported your wife's miniscule income. Actually you could continue as MFJ - report the wife's income, and take a credit for UK tax paid. Typically it's easier to keep the NRA spouse out of US tax affairs, but sometimes it's a disadvantage.
I would download the forms/tax tables etc. for the past 3 years, do the math for the additional income, use the credit for any UK tax she paid, and see how it floats out. If you owe no tax, then do the 1040X and you're golden. If the tax owed is negligible, do the 1040X and pay the tax instead of a consultant. For 2014 onward, file MFS and don't look back.