Although some form of payment can be traced back to the 13th Century, it was only in 1911 that MPs first received a regular salary. To equate that to a contemporary value is open to much variation depending on the method or index used. As examples, here are equivalents using Retail Price Index and Average Earnings...
Aug 1911 - £400 ... RPI ~£29,000 ... AE ~£153,000
Oct 1931 - £360 ... RPI ~£17,500 ... AE ~£68,000
Apr 1946 - £1,000 ... RPI ~£30,000 ... AE ~£95,000
Jan 1972 - £4,500 ... RPI ~£43,000 ... AE ~£72,000
http://www.parliament...es/factsheets/m05.cfm
http://www.measuringworth.com/ukcompare/