I think the answer that is expected from a PPL is that one draws the track line on the chart, and looks 5nm either side of it, take the highest obstacle found, add 1000ft to it, round the answer up to the next 100ft, and that becomes the MSA for that entire leg of the route.
If the elevation is above 5000ft (unlikely in England!) then add 2000ft instead of 1000ft.
That's what I was doing in 1999 and that's what I do for VFR and IFR today.
HWD beat me partly to it, but once one starts getting into non-CAA charts then one needs to be a whole lot more careful. I've seen charts (e.g. Swiss ICAO, get them by mail order from Skyguide along with the Swiss VFR touring guide) which contain a mixture of feet and metres and it's not obvious! If you are flying VFR, the hills just look a lot bigger than expected..............
It's true that there is no MSA requirement for VFR but without a planned MSA one is right up the s**t creek if the vis becomes bad (e.g. heavy rain).