I'm not from Swanwick but I maybe I can offer some info. Just in case you're not familiar with it, there is guidance on the regulations on the
HSE web site.
ATC working positions are subject to the regulations. There are also regulatory rules designed to avoid fatigue in controllers (but these are not applicable to support staff who also tend to use display screens too).. These rules are known as the Scheme for Regulation of the Hours of Civil ATCOs in the UK - or SRATCOH. There are all sorts of ins and outs but essentially it says that controllers must have at least 30 minutes of break from an operational position after (or during) two hours.
I'm not sure whether this has been formally tested with the HSE but I believe that this is far more, with respect to breaks, than the HSE would expect under the DSE regs.