I have to construct a few hundred hollow hardwood boxes. These are to
be open on the underside with some detailed but shallow carving on the
4 vertical sides and a couple of 3mm drill holes in the top and one of
the sides. I need tolerance for the holes of +/- 0.2mm. The box
dimensions will be 10x10x5cm (w,d,h)

I am looking for a service in the UK that has a computer controlled
machine to mill such an item from a solid hardwood block.

Does this seem like a sensible approach to make the item?
Can anybody recommend a UK service that can carry out this task?

Thanks,