If you find a new insurance company then it makes sense to read their policy documents before moving, and I'd recommend you ring them too and ask for confirmation in writing if necessary.
They all word their policies slightly differently but reading the documents I have, for Marks & Spencer (policy doc
here) at least, then it looks as if the condition you describe would be considered a pre exisiting condition.
However, if you've been reassured that a reoccurence is unlikely then it might not worry you if it were excluded. Sometimes it comes down to the level of support you can get from the vet; if they can argue that a condition is
totally unrelated in every way, to a previous one, then you
might get a claim paid.