Always difficult to advise on this sort of thing as it depends how much risk you're prepared to build into the connection.

Given your unfamiliarity with the place I'd say 70 minutes - 30-35 minutes for 'normal', 5-10 minutes for your unfamilarity, 30 minutes contingency.

Where are you travelling onwards to? If it's a transpennine express (their lack of capitals, not mine!) service then your Advance ticket will almost certainly be an Airport Advance ticket which does actually allow a bit of flexibility:

http://www.tpexpress.co.uk/train-tic...-explained.htm

It might be the same for other operators, or if your journey invooves a connection to another operator. Or it might not given the 'integrated' state of the rail network!

As to how those Airport Advance tickets work in practice I'm not sure. Whilst I've done plenty of plane-train connections at MAN I've never done it on those tickets. Note the bit about 'Should your flight be delayed, please ensure that you obtain documentation from your airline that this is the case'.