Quote.."Scottish frequently find they cannot maintain two-way and are probably quite used to aircraft 'disappearing', I suspect only if they suspect a problem would they try and track down the aircraft. It is largely because of this that many pilots in this area only contact Scottish if they expect to be able to maintain two way - coming from the eastern side of Scotland I don't expect to be able to....Unquote
Oban area below 2000ft can be a bit scratchy on 119.875 VHF being line of sight etc! , generally above that not a problem. I think you will find that the guys operating Scottish FIR take more care and feel more concern for you if you do dissapear off the frequency than you may think! Although not required to do so if contact is lost a few phone calls will usually establish if all is safe and well and is generally the norm..........take a leaf out of the Army Air Chopper boys at QL, these guys if only flying 10 miles or so will always use the service.
As for coverage on 121.5 this is indeed very poor over the highlands of Scotland.
The service is there to be used, it is free and the more that use it the more will benefit from it!