This is a subject close to my heart as someone who cares a great deal about the environment, and has studied the economics of the environment and centred his undergraduate Economics degree dissertation on the topic of ‘Green Behaviour and Behavioural Change'
My sense is that whilst the policy may initially strike many Englishmen as being somewhat of a paternalistic nuisance, and the levy may seem relatively insignificant in pecuniary terms, this policy is the right move; the effect has been generally positive in terms of normative and behavioural change in the rest of the UK - where levies have already been introduced (e.g. 72% reduction in plastic bag usage in Wales in the past 4 years) thanks, presumably, to both direct (financial disincentive) and indirect (market signalling, nudge) effects
What I would like to see is the levy imposed across the spectrum (not just to larger retailers) and increased (from 5p to perhaps 10p/20p), and at least a proportion of it go to environmental causes e.g. green behaviour change initiatives in particular. I would also like to see action taken Europe-wide, and in TROTW - in time, as the problem of plastic pollution e.g. of the oceans, is of course - like so many of the environmental challenges we face today - a global one