Actually Darren, if he de-limits the car the speedo will be dramatically under-reading, to the tune of 5/8ths.
Mine came with this sort of speedo face, and as a rough compromise there will be a kph "inner ring " which, if a Pete Betts de-limiter is fitted will then read in mph.
I got a replacement speedo face from Supraman in Meopham, Kent, about £30-40 but it took weeks and weeks and I only worked a mile from his garage, let alone the emerald isle.
If Irish Supra combines the delimiting with a white, or neon, dial upgrade it will probably be quicker although more expensive.
Hope that helps.