I dont think there's one simple answer to this, but here's my fixed income portfolio in the broadest sense:
ORB listed, via my broker
Funds, via platform
Investment Trust, via my broker
WiseAlpha, their platfom
Triodos Bank, their "crowd" platform - charity bonds.
Abundance - very limited exposure
Downing Crowd - their platform
With the Funds & IT's I hold typical retail investor vehicles, but also some of the more obscure debit vehciles - VSL, DNA3, LBOW, BPCR etc
There are sites, besides here, I find a help:
https://www.fixedincomeinvestor.co.uk/x/analysis.html https://p2pindependentforum.com/ https://www.creditmarketdaily.com/cmd-bond-portfolio/https://rcb-bonds.com/https://www.guybutler.co.uk/ - WiseAlpha have a free bond acadamy that's very good if you have time, and I believe the content was created by this crowd;
https://www.europeanhighyield.online/eu ... ield-blog/https://learn.wisealpha.com/If you are willing to take on FX risks, then it's possible, to hold US issues and European bonds and you'll find in both of those markets more liquidity, and success than ORB, with lower order values. I don't as it's a lot of hassle unless you are dealing in much large amounts.
Not quite what you wanted, but I hope it helps in someway.
I'm not sure there's a single list like the one you want, and my experience of using bourses to research sterling issued listed bonds hasn't always been easy.
I finding using the "IRSH" search on Investegate throws up list of companies that have listed bonds outside of ORB.
https://www.investegate.co.uk/ IRSH in the EPIC field.
You might find help in the
https://www.europeanhighyield.online/ community. I'm not a member, on the face of it they appear to be European high-yield pro's and private traders.
They also have a decent selection of printed material for sale. Most of the books are under £100 (and from memory the reports below $2000 - I may be wrong about that).
I'm subscribed to their RSS providing a weekly update of events - reporting events. It's a new feature, but that's another issue that you will face outside of ORB/LSE listed -- finding news of events and reporting. I use Visual Ping as a way of monitoring muliple holdings at a low cost - from memory, it's monitoring some 60 company sites where I have exposure to the company debt for less than $5 dollars per month.
Good luck with your seach.
https://www.creditmarketdaily.com/ig-co ... ce-charts/ provide a service to members - a list of IG (Investment Grade) bonds. Memberships is £350 per year. It might be worth looking at, maybe drop them a line before hand asking if that's a filter available. I know what my gut is telling me. I doubt it will be.