I had the misfortune to deal with Summer Green as a tenant in a flat that they were managing on behalf of a landlord. They took an age to respond to problems with the flat and to make repairs - they would need repeatedly contacting over a number of weeks before fixing even the most major of problems.
When it came to checking out, they attempted to charge us an unbelievable £250 for a deep clean of the flat, when the checkout report had clearly stated only a small area needed to be cleaned. When we challenged this, the gentleman we dealt with was rude, extremely aggressive and downright threatening. The kind of person who replies in red capital letters to any email, and then shouts at you on the phone.
I would not recommend that you deal with them at all - they're a disgrace.