There are two 1/2" square steel caps protruding through holes in the
kitchen tiles, just about flush with the surface of the tiles.

I think that there must have been one of those gas "hot water on demand"
things above the sink in the old days.

I could just about get away with tiling over the existing tiles to
totally conceal these. However this does seem a bit naughty.

I presume that the gas is still connected hence the plugs.

Is it permissible to just tile over or will I need a CORGI person to cut
the pipe and cap the supply pipe lower down (Behind the sink) so that
this connection and pipe can be removed? Can a CORGI engineer cap the
pipe in a way that it can be plastered and tiled over?

The pipe that emerges from the gas meter, simply goes into the concrete
floor and then, somehow branches off for this connection, the boiler and
also an unused gas cooker point (also capped off).

Thanks for any advice.

Steve.