NatWest just told me savings bonds covered by extra 48K in addition to the FSCS 50K

Aegis

There are ways to get additional protection outside the normal £50k for savings, including the use of life wrappers with cash investments held inside them. These can then fall under the FSCS insurance scheme rather than savings or investments, which (from memory) protects roughly 90% of the value without a limit.

However, they're usually fairly complicated in terms of taxation, and they probably don't offer great rates. The HSBC version of this was the Guaranteed Income Bond, and I imagine that other banks have a similar product. Be aware though< staff generally know next to nothing about the specifics of these products.