Don't know where Holdens Farm is but there is an organisation called South Manchester Ringing Group who might be able to help and might want to take the site under their wing if access is straightforward
We seem to have more swallows than ever this year At Holdens Farm. Someone from I think the RSPB used to come and ring the young, they have not been for 7 / 8 years do they still do it ? If so who do I contact please ?