Dear Carrot,
Slightly off main query.
Not my product area or UK knowledge but from a Dutch auditor in another thread, application of chlorine is apparently prohibited for veg. / fruit there and similarly for imports.
Was another thread from Luxembourg approx. 2yrs back (Hi Max!) and he was using (from memory) a similar compound as swimming pools (...isocyanurate) but that does not currently seem to be so popular for technical reasons (quoting FAO via a slaughterhouse thread here).
Other European countries ??
I looked through several current reviews of the veg. / fruit scene (mainly US oriented) via an ISO 22000 query and a few other products came up such as electrolysed water (?), organic chlorine (not exactly the one above), the objective being to achieve higher bacterial killing power (ie > 2log) + without the known hypochlorination side-issues. ClO2 seemed to have ultimately been found relatively non-user friendly (perhaps not so surprising from my memory of investigating its use for plant water supplies, was pretty expensive also).
Rgds / Charles.C