Getting to Bishop Wilton Wold (known as Garrowby Hill by the locals) and Normandby Top using public transport is going to be both time consuming and difficult.
G/TW-005 - Normanby Top.
For Normandby Top, one option could be the “Humber Flyer” bus (run by the Stagecoach company) from Hull to the Humberside airport and then a Taxi from there - agreeing that he will pick you up say, 2 hours after he drops you off. Normandby top is not too far from the Humberside Airport.
Alternatively - instead of a Taxi you could take the 53C (run by the call connect company) bus from the airport to Caistor and walk south out of Caistor on High Street for about 2 kilometres and you will be within the 25m vertical activation zone for G/TW-005. The driver might even drop you on that road if you ask him - but you’ll need to walk back into Caistor for the return journey.
Note however you have to book a place on that 53C bus “MUST BE BOOKED more than 2hrs in advance. Phone 0345 234 3344.” It’s effectively a local airport shuttle service.
http://www.traveline.info/ - click on “plan your journey” and then select Hull and Caistor.
G/TW-004 - Bishop Witon Wold
The buses that go near Garrowby Hill, are normal buses from East Yorkshire Motor Services.
The Pocklington to York bus goes to Bishop Wilton, but that’s at the bottom of the (steep) hill and you would have to get from Hull to York or Pocklington on another bus, to connect with this route. If Terry can meet you in York and take you here - that’d be a good solution. There are trains from Hull to York every couple of hours (there are also buses).
When are you intending to be in Hull? - is this a weekend visit or during the week?
Good luck! 73 Ed DD5LP (born in Kingston upon Hull now living in Germany).