When fitting outside taps where the problem is similar - getting the tap
to
face downwards when screwed into a wallplate elbow constrained by the
direction the pipe is coming in from(*)
(* why they don't do wallplate straight couplers, like a 1/2" BSP
Female with a flange with screw holes in it, so you can just bung
the pipe directly back through the wall with no problem of
orientation - or if they do, where to get them - I don't know)

Like this one at £1.50 inc VAT. (Toolstation.com Part # 33291)
Small order delivery charge is £5 but you can collect from the branch on
Whiteladies Rd in Bristol.
350mm so should be long enough for most walls.

--
Toby.

'One day son, all this will be finished'