That is why I provided the link to Mini Spares. Their kit plus the separate conversion harness totals 245 GBP which is $385 at today's exchange rate. You would have to add shipping and sometimes UPS charges a handling fee to move packages through Customs. That will bring your Mini Spares totalled price up another $50 or so (guessing based on past purchases). When you add shipping to the Moss kit you can see that Mini Spares is very competitive. Mini Sport probably offers something similar if you want to compare other U.K. vendors.
Regardless, before you buy check the TPM number of what you have against what is in these kits. If the TPM numbers are not close, the speedo will be inaccurate. You can figure out how inaccurate using simple math. For example, if you have a Mini with a 1376 TPM number speedometer and the kit contains a 1280 TPM speedo, take the ratio of the two numbers and you will know the error. In this example, your car turns the speedo cable at 1376 RPM at 60 MPH. If you hook up a 1280 TPM speedometer it will be turning "faster" so 1376/1280 = 1.075. That means instead of showing 60 MPH your speedometer will read 60 x 1.075 = 64.5 MPH. Your odometer will also read high by the same percentage.