how can you know for a 'fact' that some colleges offer part time PGCE's but not which ones? Did u read something somewhere that said that 'some colleges offer part time PGCE's but we are hiding the information from you'?
You would be lucky to find a 'college' to offer postgraduate courses as this is usually the realm of universities. And the institution would have to pass rigourous QAA tests to prove they are able to deliver the course to required standards.
And with 4 years university admissions experience i would be highly dubious of 'colleges' offering postgraduate programmes. Check the validation of the institution and it's courses before making a decision.
As part of your 'teacher training' try doing a little more research than Google perhaps.