Speedo and odometer not working

Hello,

I have a 53 plate 1.25 ford fiesta (non-ABS). Last year my speedo worked intermittently (engine light was on most of the time). I replaced the speed sensor and hey presto no more problems.... The problem started again last week with the intermittent problem, it now doesn't work at all. No mileage and no speedo for the past 4 days. I pulled out the sensor this morning and checked the seal and the attaching cable, no obvious problems. Been reading that it could be an ECU problem, hope not! Need to MOT my car this month so would love to fix this myself (if only temporarily) to get it through. If it is the ECU, is it a good idea to get one from a place like ebay for example?

Any ideas?

Thanks in advance.