Thanks for your reply Sam, it has come about as my husband started as a sole trader last year and failed to register and then failed to complete self-assessment, HMRC now want to know what we have been doing since we came back to the UK four years ago. The first two points you mention do not apply and we although we did have rental income from a property in the UK for the first year we were abroad I can't remember how much it was or for how long we had it! They have asked for french bank statements to "assist them" but I have not kept them so cannot prove anything.
No we didn't declare it as we were abroad (should we have? oops), yes we sold the property and no managing agent was used.
Thank you Sam you've been very helpful, can you just clarify something, I understood that you only pay capital gains on a second property so why would be liable for any gain on our UK property? Would our french property therefore be classed as our main residence - even though it was not habitable for 6 months and we lived in a caravan?