£36.82 (33% off - RRP of £49.99) for a 12 month PlayStation Plus membership (UK). This is the cheapest price that I have found, next cheapest being £39.85 at ShopTo.
I had not used Instant Gaming before, so was a bit wary. But as my subscription literally ran out today, I thought I would give it a go.
The voucher code was displayed on the webpage immediately after my payment was processed. I logged onto the PlayStation Store and redeemed my code, which went through straight away - no problems. I’m now a paid up PlayStation Plus member until 16/10/2021 - happy days.