You can only usually only get this offer as a new subscriber, however I get a discount through my employer and looked into it (use the link)
Initially they said I would not be able to have the 15% discount applied because it's for new customers only, but once I told them I would cancel and change to the similar Scottish hydro service they put me through to another department where the 15% discount was given.
The link is for an MOD affiliate program but they do not ask for any employment details when negotiating the discount. I beleive they do similar discounts for other public sector workers so use your imagination people!
0845 607 1748 for the homecare team