Phil Addison wrote in message ...
That would make it prime candidate then - cheap, easy to apply and
durable then. Is your preference for body filler because of its better
adhesion to the sill? I must say I would not relish working with the
latter if an easier alternative would do the job.
Body filler is also cheap if you get it from a car paint trade outlet.
Around a tenner for 3.5 kgs IIRC. It does have better adhesion and has the
advantage of being waterproof without being tacky.
However it is a bitch to use in this sort of situation. I find loads of
hardboard scraps useful. Use them as a base for mixing and as an applicator,
and chuck them for each mix. Only mix what you can apply in, say, 2 minutes
(which isn't a lot for detailed work).
A basic resin without filler (fibreglass resin) is very easy to use and has
the same benefits.

Thanks, found Pliolite here http://www.eliokem.com/prod_coatings_plc.php
The adjacent walls are rendered in a yellowish spar, so a light colour
would be OK. Think I prefer the idea of a specialist paint for longer
life though.
Johnstones had Magnolia on special offer recently ("Stormguard"), which made
it virtually the same price as standard masonry paint.
As an aside, it occurs to me that those cheap paving slabs are "concrete",
yet water goes straight through them.