Thanks chaps. I was famous at school for making the class' worse ever birdbox (not a solitary tit ever bothered with it when it was hung in the garden). So I won't be embarassing myself by trying to make a workbench. ;-) Sure, it looks so easy in the videos, but...

Had a look on ebay and most don't have such sturdy legs as 4x2", but this type seems better than most: http://www.ebay.co.uk/itm/281942662716 - and I sould certainly be able to add some additional diagonals for bracing, if necessary. I could also replace the relatively thin top with a kitchen worktop, as suggested above.

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On bits, the #1 most common job for me is a board with lots of round 2.9mm holes and then a much smaller number of 3.5mm and 10mm holes. So for machining speed I was planning to make the 2.9mm bit my 'go-to' and buy them in some quantity.