This is technically a 'student deal' that I found via Unidays however link works with no unidays login necessary.

Alongside the usual 14 day Now TV trial, when you trial Sky Movies via this link and allow one month's payment at £9.99 thereafter redeem a free £15 Topshop voucher. As such, get 6 weeks of movies and the voucher. If you regularly shop for fashion items you're basically getting £5 return and free movies.

TopCashBack for next 6 days only: £12.60 cashback with the Sky Cinema Month Pass - whether this will work considering it is 14 days then one month I do not know, and of course whether it will be granted alongside voucher - though this isn't a code as such.
https://www.topcashback.co.uk/nowtv/?ref=tb&utm_source=www.nowtv.com&utm_medium=toolbar&utm_campaign=toolbar

This is for new Now TV customers (or a new email address).

Of course cancel any time after the first payment (must make at least one month to claim voucher) however they have made it easier to remember as when the first months payment goes through they will email how to redeem voucher - if no longer wanting the services simply cancel at the same time as redeeming the voucher! A handy reminder.

Unidays link:
https://www.myunidays.com/GB/en-GB/partners/nowtv/view/online