Defender TD4 1997. Has had occasional starting problem for years but would go months without a problem. Turn key, complete silence, no click, nothing. All other electricals work fine. Sometimes starts after 2 or 3 tries but has taken up to an hour (aaaargh). Starter motor renewed last year - no better. Ignition switch changed 2 weeks ago - now worse if anything. Starts from cold in the mornings no problem but issue seems to crop up when cooling down or after a short run e.g to get fuel - embarrassing to get pushed off the pumps! Any ideas?