On 14/02/2011 20:39, Jethro wrote:

I pity the poor sod who tries to drill holes where the broken screws
are - although I suspect that when it needs maintenance or
refurbishing, the poor sod will be me.

[...]

What would people here do ? Or is the only guranteed answer to smash
the concrete to pieces, and relay where needed ?

Assuming the broken screws are flush with the surface[1] and not causing
anyone any harm, then I'd leave them the hell alone! If and when they
ever do really need to come out, then worry about it at then - with luck
it will never happen. (Read the current thread where loads of folk have
successfully attached their lavvies to the floor with just silicone)

David

[1] If not, then you've guessed it - ANGLE GRINDER time!