I don't think I can justify it as a career break because really it was just due to some bad decisions on my part. Oh I didn't see that but to be honest since I'm not attached to a University I kind of thought that this would be the only way of getting the grant funded i.e. being named as a co-investigator and then applying for the project. I think I might approach some PIs that may be interested in the project as they may have better ideas of funding than I do. Plus they may know if there are any local schemes, as you suggested, that I may be able to apply for. Many thanks for your help

Thanks for your answer Phil. Unfortunately it's been too long since my viva to be eligible for most Early Career fellowships, but after your comment I did a search and noticed that RCUK offers a grant for postdocs at whatever stage of their career (as long as they are not PIs). I may try applying to them.

I just applied for an advertised Postdoc position on the University's website. That's the norm in the UK.