Nice bench - looks like you've put plenty of thought into it, and how it works for you, but I think you're making a mistake if you think that everyone has the same issues that you do with existing portable benches.
By definition, you're trying to sell a finished product (with all that entails - warranty issues, returns, VAT, carriage etc...) to people who are good at making things, and for whom the existing portable benches don't work well enough; how big a market is that, in this country? I see lots of guys using a pair of sawhorses with an mft-style top, or those keter workbenches, or just old workmates, or maybe - being good at making stuff - they made their own to suit their needs. Here's mine, from 2008:-
I made it narrow so it fits on the front paths or hallways of the London terraced houses I mostly work in, with pull-out hooks for doors. Made it short to fit in my van, and it folded up so you can easily carry it one-handed. I still use it today (not as pristine, mind!) because it's perfect - for me. For others, it may be too small, or not sturdy enough, or too low, or whatever. Point is that you've made yours to suit you - it folds up so it fits in your trailer, for example - and not everyone wants what you want.
On top of that, you're asking a few hundred quid for something that, with respect, a lot of people may feel they could easily make from a couple of sheets of ply or MDF. Now maybe there's more of a market there than I think, but even Ron Paulk, after selling 'thousands and thousands' (
video) of plans for his benches since 2011 has only just (last month) announced availability of a smaller bench made in association with FastCap, available in kit form or fully assembled. Not to discourage you, but here in Britain with a smaller addressable market and higher costs, I think a one-man-band startup would struggle to sell in significant numbers - but totally happy for you to prove me wrong!
Have you considered selling plans? I feel it may be a simpler way to start.
Best of luck with it - let us know how you get on.
Pete