Having looked at the Local Govt Ac 1972 Schedule 12 Part 3 I cannot see anything which would prevent the Councillor being allowed to speak. However, he or she would not be able to vote in any poll taken at such a meeting. What might come as a surprise is this though:
The chairman of a parish council shall be entitled to attend a parish meeting for the parish (or, where a grouping order is in force, for any of the parishes comprised in the group) whether or not he is a local government elector for the parish, but if he is not such an elector he shall not be entitled to give any vote at the meeting other than any casting vote. So this means that the Chair of any Parish Council could attend anybody's Parish Meeting and if a tied vote arises, could be the ultimate arbiter of the vote. Highly unlikely though.