I spent the 1990s employed by several offshore bond providers as a product designer, and continued doing similar work for a good few years after that as an independent consultant.
These products have been around for a very long time - certainly since the 1980s, if not before, and the tax legislation dealing with them is well-established. Apart from closures of a couple of blatant loopholes and some peripheral tidying, their UK tax treatment has been stable through numerous changes of government, and can be very favourable to some investors, as I’m sure your IFA will already have outlined to you.
Historically the biggest centre for hosting these products has been the Isle of Man, where a number of British household name insurers set up subsidiaries in the 1980s. However since then most of those providers have been the subject of takeovers and management buyouts, and in my view and based on my experience in recent years the quality of service in that jurisdiction has fallen way below any acceptable standard.
For optimal quality of service and investor protection if I were you I’d want my IFA to recommend a Luxembourg provider.