The new tax levy on plastic bags is now in force but is aimed predominantly at larger retailers with over 250 employees.  It applies to new bags of 70 microns or less - which is quite thin - and with handles.

Exempt polythene bags must be multiple use ones used to hold free promotional material and with a minimum size of 404mm x 439mm in either width or height [excluding handles].

For some applications a heavy gauge polythene bag is still the best solution as they are water resistant, can be re-used and have a large branding area.