I've had an email from the ecologist at North Tyneside Council regarding the vegetation removal at Brierdene and it's all good:
The grassland has been managed as any other hay meadow would be, by an
annual cut and rake off, which helps deplete the grassland of nutrients
and diversify the species in the grassland. This is standard management
practice for wildlfower meadows and would normally occur at the back end
of the summer (september/october) depending when it is dry enough to
take a cut.
If you had been to this site a number of years ago, the grassland was
very poor quality with little species diversity, because it was not
being managed appropriately. The group at Brierdene have been awarded
several pots of funding from various avenues and have proceeded over the
last few years to introduce wildflower seed into areas which were
becoming very rank and to then manage these areas (by an annual cut and
rake off) to improve species diversity. (They have recorded a large
increase in wildflower species as a result).