It depends where you are living. In London 40K is a lot less attractive than in York (where I live and work) where it is probably very good, and in somewhere like Grimsby it might be considered particularly high. The cost and hassle of working in a particular place (i.e. either rent or property purchase prices, and/or the convenience/availability/cost of transport options, access to good social facilities, and so on) make a huge difference and vary by a surprising amount from place to place even within a relatively small country and this factors into what an acceptable salary is. Of course a good benefits package can affect the acceptability of a given rate significantly too, potentially offsetting the geographical differences - you need to consider a lot more than the one headline figure when judging if the offer is fair.