Many years ago (10 years +) my business failed (non-limited) and I was forced into bankruptcy. I ended up going personally bankrupt. I now own a limited company which is doing well and am thinking of selling it. Could my past bankruptcy affect my ability to sell? Thanks
No. The limited company and you are entirely separate legal entities.
Further, since your personal bankruptcy will now be discharged, it won't appear on the Bankruptcy and Insolvency Register so there's no way that any potential purchasers could even find out about it.
I have read a few share purchase agreements and this seems be a question that is asked on the samples I have seen. Why would it be asked if its not relevant
There may be concern that a bankrupt might try to sell shares which should go into the bankruptcy. That may be why the question is on the form. However, your bankruptcy was so long ago that I assume you were discharged years ago and have no further obligations to the Insolvency Service. If that is the case I don't see how you could be affected.