My 1974 ABC rail guide shows a 2345 SuX Euston-Barrow sleeper service arriving 0553 on Tues-Sat mornings, 0650 Sunday morning, no service Sunday night into Monday morning.
In the reverse direction, 2048 SSuX Barrow-Euston arrive 0223 (berths available until 0730), 2053 SuO Barrow-Euston arrive 0227 Monday morning (berths available until 0730).
Looking at the normal train service, it appears that the seated coaches ran 7 days a week, while the sleeper accommodation missed out one day (no sleepers northbound Sunday night or southbound Saturday night).
There was also a through daytime service: 0755 Barrow-Euston arr 1219 / 1805 Euston-Barrow 2243
2nd class return £13.57. According to the Bank of England inflation calculator (
https://www.bankofengland.co.uk/monetary-policy/inflation/inflation-calculator), £13 in 1974 would be £133 in 2018.
A similar journey today (0746 from Barrow, 1830 back from Euston) would be £113.60 Off-Peak Return.