Information leaks are always useful to scammers, extortionists, blackmailers etc. It's one reason we protect financial info.
Like the other poster said, VC money isn't really needed, though the process of getting accredited with the FCA is more than just paying for a license. The Open Banking Implementation Entity (or just Open Banking Ltd, whatever they're calling themselves at the moment) may be able to help you go through the accreditation process if you approach them, they were certainly talking about doing that for people a couple of years back.
And before that you can sign up to their public sandbox service as a "Technical Service Provider" to start developing against the ecosystem, for nothing (I've done this though I've not really used the capability for anything).(You may need a Ltd company for this, can't remember off the top of my head)
Restricting API access doesn't help. There are plenty of idiots out there who willingly install remote access software on their computers/phones, fall for "authorized push payment" fraud when scammers tell them to move their money to a "safe account" or to pay overdue "taxes" (gullibility taxes?) over the phone and even use the two-factor card readers despite the "do not use over the phone" text being printed right on them.
I'm not sure how read-only API access would benefit scammers (if people can be tricked into granting API access, they will usually just as well install remote access software or just do the payments manually) but it would open up a nice field of self-contained, on-device money management apps that don't need significant corporate (most likely VC) backing with all the (usually) nasty ramifications that entails.