I've just bought a Briel espresso machine by mail order from France. It
has a standard European two pin plug with receptacle for male grounding
pin. It runs on 230V and load is 1600 watts. The only adapter I can
find online is Maplin's euro convertor but that shows a max load of 600
watts. Can I just cut off the plug and fit a standard UK plug onto the
cable?

UK voltage is now nominally 230V +10% -6% so it should be fine as long
as you can sort a plug out.