At October, 1970, the provisional figures of average weekly earnings of full-time manual workers were £28 Os. 11d. for men aged 21 years and over, and £13 19s. 10d. for women aged 18 years and over. Between October, 1965 and October, 1970, average earnings of all workers covered by the regular inquiry rose by 45.9 per cent. and the general index of retail prices by 26.4 per cent. https://api.parliament.uk/historic-hansard/commons/1971/jan/...

So it would have been around a decent chunk of your weekly wage as an average worker, it sounds like. I think what we would need to know is how much excess income someone would have for something like that at the time.