Keeping Things Cool. - 

The standard Mini radiator struggles to keep a mildly tuned 1275 cool so on a Turbo motor it's no use at all.
The new super 2 core type radiators are a much better item. If this is not enough an extra radiator can always be added from the heater take off on the end of the head, or if there is enough room a front mounted radiator is the best option, the unit from the 96 onwards Twin Point Injection Minis is ideal, though i have always managed with the 2core and a 72 deg thermostat. 
Even with a water cooled Turbo and the radiator is still coping.

I'm now running a dry deck system on my new engine build. The water ways in the block have been plugged as shown below, the head has been drilled on the end & the adaptors shown below fitted. One in the head & one into the block after removing an end core plug. The temperature is far more consistend now.
Dry deck adaptor kits are available from the shop/store.

See block modifications for further info on dry decking.

Dry deck adaptors & hose.

This kit is available form the shop.

Waterways are tapped & plugged to form a dry deck setup.

This picture shows the block face where the water pump mounts,
grinding the shaded area away helps water flow to the back of the block.
This is easily done with a carbide bit in a drill.

A front mounted radiator from a TPI Mini.

Small, compact, but very efficient.

Cooling is more often a problem at slow speeds when in queues or slow moving traffic on hot days. In these situations the standard fan is not usually adequate. It's well worth adding an extra fan mounted under the inner wing as shown in the picture. They can be picked up very cheaply from the scrap yard, the particular one I use is from a Metro.
You must make sure to wire it the right way round so it sucks the air out from the engine bay.