Whilst I do agree with paying for what you get - £1700 on a mattress seems mental.
But you spend a third of your life on it.
We've had a memory foam mattress for about 6yrs now. Paid about £300 off ebay. 8 inch deep top 4" high density memory foam.
We've always wondered whether a Tempur would be better but of not we've wasted £1500.