In my experience - I had a policy with WD many years ago, on which I had some success - the dealer / mechanic being on board, and having the stamina to make the case for you on the 'phone, is always critical. I remember when my SID started to fail. The policy said it would cover the 'trip computer' but not the 'stereo/radio panel' or something like that. I briefed my guy and heard him make a call which went something like:
'The Saab Information Display has failed. It's a trip computer.'
'What does it do?'
'It's a trip computer.'
'What functions does it perform?'
'It's a trip computer.'
'Is it part of the stereo system?'
'It's a trip computer.'
'Does it show radio stations?'
'It's a trip computer.'
'OK, here's your authorisation number...'