Does this 150 have long range fuel tanks? if it does then if you fill them full there is no "we" on this trip.
My cessna holds 88litres of fuel with standard tanks and burns 23lph unleaned in the cruise which at absolute best will give you a 4hr duration. it burns 33lph in the climb which averaging it all out gives you an effective range of 3:30 with no reserves.
I always allow a 30min diversion time when VFR and 45mins when IFR subject to the closest airports on track being within this flying time.
So in a nutshell my rule of thum is for planning purposes 6GPH gives me 3hrs useable and the rest for reserve.
I have very accurate fuel consumption figures for my aircraft based on a FS450 fuel computer linked to a GNS430 and several hundred hours of practice.
In your scenario I would probably be refueling twice for sanitys sake. If I got to East Mids with half tanks then I would be concerned at making Humberside without a refuel. And I would probably refuel at Humberside as well.