I've noticed a descrepency between the Reward Flight Calculator and the actual avios/cash when making a booking. Looking at fligts to DME, the Reward Fligtht Calculator quotes 20,000 Avios + 50pence for a one-way Peak flight, but when attempting to book this I am been charged 25,000 Avios.
I'm, not sure how wide spread this issue is, but it has only just crept in when variable Avios pricing was introduced.

Also, now that variable pricing does exist - how do I work out the points required for a Amex 241 booking? Do I have the option to choose less Avios more cash (or visa versa) or is there still a fixed rate for these bookings?