By Guy Taylor Struggling rail operator Avanti West Coast has signed a rest-day deal with its train drivers that could take average yearly salaries to nearly £100,000. The group, which runs routes on the west coast mainline between London, Birmingham, Manchester and Edinburgh, will pay drivers £600 to work overtime, alongside the typical four day week. Under previous arrangements, train drivers had received £125 and an hourly rate for working the extra day. Average salaries for the four-day week typically come in at around £70,000 per year. The deal, which was first reported by The Sunday Times…