Terminology note: England on its own didn't have a monarchy after the Treaty of Union with Scotland in 1707. It was the Kingdom of Great Britain.

I believe the usual definition of "elective monarchy" is that, for each vacancy, some body votes and elects a successor. In that sense, no, Great Britain did not have an elective monarchy.

It's true that Convention Parliaments called William and Mary to the throne (one each in England and Scotland). It's also true that the English parliament passed a statute called the Act of Settlement of 1701, which (as amended) has controlled the succession ever since. It's true that the current Parliament, and a lot of Parliaments since then, could pass and have passed laws changing the succession.

Nevertheless, succession to the throne since William III and Mary II has been automatic on the death (or death for succession purposes of Edward VIII) of the predecessor. No vote of any sort takes place. The first meeting, that of the Privy Council, simply proclaims the new sovereign, and so with all further acts.