If you are going to Dublin after the c to c it would make sense to start in RHB.Getting a train from RHB to St Bees would be quite expensive as it involves using three different companies.When going to RHB it might be an idea to get a ticket from London to York and a seperate ticket from York to Scarborough,might work out cheaper if you can't get a special deal.Buses run from Scarborough to RHB,usually every hour.