Thanks nux. I may have got my maths wrong, but this is my reasoning so far.
For the two nights:
Best available rate including tax: 250 EUR.
Points + cash including tax: 20,000 + 150 EUR
That's 100 EUR for 20,000 CC points, which is 0.5c or 0.41p.
Considering that the conversion rate from MR to CC is 1:3, wouldn't that mean getting 1.23p per MR?