I'm wanting to put a radiator in beneath a window in my bathroom (or
rather I'm getting a plumber to do it). Being a somewhat, errrr
characterful house, the internal window cill is not level. If the
radiator *is* level, and is just below the cill, it looks awful,
because it highlights the fact that the cill is wonky.

I want the plumber to put the rad in so that its top is parallel with
the cill, and bugger the levels. However he is strongly advising
against this on the basis that it won't work, there'll be air locks,
etc. Is this right?? I can see no reason for great problems. So long
as the bleeding valve is at the higher end of the rad then any air
should be easily bled, and I can't see a problem.