As for jamming, you must know that the law has an exception for small premises with acoustic instruments.

I do know that there is not an exemption to the requirement for Premises Licence entertainment permission in small premises and non-amplified music - either social jamming or in conventional performance. There is a rather nonsense S177.

For S177 the premises first have to apply for entertainment permission and then the conditions that can be placed upon the non-amplified music between 8pm and midnight are then only limited to two of the main objects of the Act; the prevention of crime and the protection of children from harm.

This very limited provision only applies when the local authority has imposed a safe minimum capacity of 200 people or less and S177 can be very easily avoided by them altogether (as I have found locally) by the very simple process of the local licensing authority not imposing any safe capacity.......For S177 only applies when a safe capacity is imposed.

Perhaps we are less free to make music than we are led to think we are?