They don’t advertise political party membership like this any more
This is from an early recruitment leaflet for the SDP issued in 1981 which had a rather dated way of describing the cost of joining a political party:
(The SDP was a new political party formed mainly as a breakaway from the Labour Party, although it also attracted one Conservative MP. It formed an electoral alliance with the Liberal Party for the 1983 and 1987 general elections. The two parties then merged to form the Liberal Democrats.)