I fly all over the place and on 99% of occasions the only holding I do is at LHR (my base). Other operators may not be so used to the fact that for 70% of the day you'll have to go into the hold at LHR, so you have to imagine being in their shoes. Also some pilots may be using the latest charts which now include an intermediate approach (whereas the old charts from 5 years ago merely had the STAR's and final approaches). Finally some people may just be having finger trouble - forgetting to press the 'execute' button or similar.
How to solve your problem is another matter. The best suggestion I have is to get the airlines involved in the misdemeanors to write the information in their RIM's (Route Information Manuals) if they have them, or get them to write something in their briefings (for example a NOTAM) to highlight the potential problem. The entry should include 'pilots should generally expect to hold at LHR, and if there is any doubt then one should clarify the clearance limit/holding pattern with ATC' or similar.
Alternatively perhaps you guys can have a leaderboard of airlines that make the mistake - much like airlines that do CDA's, and publish the results!
Having more crap on the ATIS is not an option I would like to see used - the weather takes up 2 lines, and the disclaimers these days seem to take up 20 lines! Wing tip clearance, readbacks etc.
Good luck with the challenge.
P.S> I have trouble with holding patterns in the US - "hold 070 SW patterns" is just really confusing to me especially after 12 hours at work!