The people (a very small group) who really couldn't stomach the successful introduction of the TLM at Blackfen left the parish - but since Welling parish church is about 10 minutes away and Sidcup parish church is about 5 minutes away, this isn't particularly surprising, and quite a few people cross parish boundaries anyway because of convenient bus routes. Other people crossed over into the parish, attracted by the reverent style of worship at Blackfen (and not just at the TLM.)
In view of subsequent events, one might question whether the specification of the time of Mass rather than the form was deliberate. After all, Mass continues to be offered at 10:30am on Sundays, just not in the Extraordinary Form.
UPDATE: It would appear, from one of the comments I have received, that something along these lines was the case. Fr. Fisher has declared in the parish newsletter that he had not intended to end the Extraordinary Form Masses and was surprised by the fall in numbers... however, in view of this drop, he is going to have to consult with the Parish Council. Since the chairman of the Parish Council, appointed just over a week into Fr. Fisher's tenure, is known to be strongly opposed to the TLM, the outcome is predictable. Be that as it may, the intention to cease the TLM provision from the end of September had been announced from the pulpit on Fr. Fisher's second Sunday.