i think castrol GTX is up there with duckhams classic........chris,use cheap oil if you want.........................in the long run it aint cheap mate.
Ross,millers classic is good also,but i dont have personal experience of it.
my choice is duckhams(£10.00ish 5 liters),i have used it since i was 17 yro sprog on all sorts of older cars,but,i do use a semi syinth in the rangy,and full syinth in the bikes.