The only HG compatible 11-speed cassette I'm aware of with a 36T sprocket is the SRAM PG1170 11-36, not sure if ~£70 meets your definition of affordable.
34/32 will be fine for you, if you need a lower gear, the sugino chainset from hubjub would work, or make an ugly solution by getting a triple and putting 46/30 to give a good range with 11-28 without too big a jump.
The only HG compatible 11-speed cassette I'm aware of with a 36T sprocket is the SRAM PG1170 11-36, not sure if ~£70 meets your definition of affordable.