Official answer - in the UK there are no back-course approaches published and yes
some locs are fixed to reduce the signal strength behind the antenna (I think improved antenna designs now makes this less common). It's hard to know whether the back-course signal is accurate 'enough', it simply isn't flight-checked because it is not used for any procedures.
It's interesting that you ask though - a while back I (a simple controller) mentioned that I thought some crews set up the ILS/loc on departure to use the back beam to assist in staying on the centreline if required (not wishing to open another debate but this would be if the clearance was to climb straight ahead). This comment was based on discussions with locally based crews and, in the old days, a fair few trips on the flight deck. It also helps if there is a need to return quickly. It all seemed perfectly sensible to me. The response from some pilots was along the lines of "get real". I'd be interested in any pilot comments.
P.S. JSJ, the idea of following a glidepath back-course is slightly worrying.
