Trying to create another record from EPOS transaction.

What EPoS software are you looking to use?

We're hoping (!) for it not to be specific to a particular software but be able to capture the key transactional details irrespective. If that is an aspiration too far, we'd have to focus attention on the most widely used software in the UK as a start point. However frustrating that would be. Ideally, I want to convert the transaction data to a bar or QR code.

You may be 'hoping', but that is totally pointless. In order to capture any data from a specific piece of EPoS software you will need access to the API they use (assuming they have one) to be able to get the sales data sent to your app as they happen.

I can't see a single valid reason for you needing this however, as most EPoS packages have the ability to do something with the sales data - generate a receipt, email it, or similar.

As for the "most widely used", that's a very open thing as it depends on what environment you are going to be targetting, but most of them will not give you access to their development tools without significant cost and very good justification.

Thanks for the input, Simon, as I think I alluded to, this is a new application and isn't specifically anything linked to the financial transaction, although it does need that data for a secondary purpose.
So, sounds like an approach to the EPoS package providers is going to be the only route forward.
I'd expect there to be many companies in this space but primarily we're looking at food/beverage retail, fast food outlets, that space more than any other.
I think we may have sufficient justification if this proposition is seen as being a positive differentiator-we'll see.