I am concerned that anyone of any nationality can be coerced into believing that fighting is in anyone's best interests.
I am not concerned about shopping, or indeed going anywhere my daily life takes me.
The issue of trying to stop young men from going abroad to fight is difficult - none of them are going to admit the purpose of their visit, and holidaying in their country of origin for extended periods is common practice for UK Asians.
I would suggest that any British passport holder who is found to have engaged in hostilities should have their passport and citizenship - where appropriate - revoked.
But again, proving it will be extremely difficult, and already you can see the ECHR gettng into gear.