Was just looking on ignition car parts site for new dizzy cap and rotor, and noticed that they do abs sensors.
They didn't pick up my reg on the search, and the mc2 isn't listed in any of the compatibility charts, but I did a search on the honda part number for a rear sensor and it took me to this page
http://www.ignitioncarparts.co.uk/PartDetails.aspx?s_pc=SMP-60094&s_vid=
Like i say, a couple of ms are listed (diesels) but not others, so be cautious and check before buying, but £73 for a new sensor is the best price I've seen... And I've done some looking over the years.