Best Mitre Box

[rob]

Tile Trim (metal) is becoming very popular in NZ making mitre cutting a very important part of my jobs.
What is the best mitre box out there in the UK for cutting both PVC & Metal Trims? any ideas on where I can get a good one?

 

[pjtiler]

internal mitres are ok but see if you can buy external corners as mitres are to sharp