An Off Peak return from Manchester to Milton Keynes is valid for arrivals into Milton Keynes at or after 1030 and is priced at £51.90
An Off Peak return from Newcastle to Manchester is valid for arrivals into Manchester at or after 0930 and is priced at £59.40. To arrive before that TPE want to rob you of £78.50, so don't let them. Newcastle to York Off Peak is valid for departures after 04:00, and is priced at £33.70, and a York to Manchester Anytime is a reasonable £29.90.
TOTAL = 33.70 + 29.90 + 51.90 = £115.50
This is just £2 less than half the price that the idiots at Cross Country think you should pay for this journey. XC set the fare even though the most sensible route is TPE / Virgin via Manchester, and XC have the most restrictive tickets in the country.
Recommended journey:
Newcastle 0613
Manchester Picc 0905
Manchester Picc 0915
Milton Keynes 1046
You can get the 0613 from Newcastle at York (0740) leaving a few minutes later at 0621, you have 18 minutes at York (arr 0722), I'd recommend doing this as there is an unofficial potential connection at York leaving at 0723 that gets you to Manchester at 0851 which gives you more time to make the connection at Piccadilly. You probably won't make it but it's always worth a try.
On the return you can depart MKC between 0900 and 1514 (inclusive) and at or after 1901. There is no restriction on when you can leave Manchester or York.