You can find the link here.
I just did a quick research for a hotel in Birmingham for next weekend and indeed Ibis Hotel in the city centre was £25 per night. The same hotel without going through the discount link was £51 per night. So you are basically saving 50% of a hotel stay in this case.
Accor are currently running another offer for 5xAvios which can be well worth signing up for before you book your hotel stay. This way you will receive 5x more points from your stay which then you convert to Avios. 🙂
You can find this offer here.