There are some hotels that offer special rates to guests attending a wedding at the Assembly Rooms — there are more details here. Please do let us know if you have any issues with these hotels around rates or having to identify which wedding party you’ll be part of. There are also a number of smaller hotels and bed and breakfasts in and around Newcastle, particularly in Whitley Bay, Cullercoats and so on.
UPDATE: A number of people have found that most of the hotels are now booked up. Quite a few folks have found place at The Albatross, a hostel in the centre of town. Might be worth looking into if you’re still struggling.
There’s a good metro system that runs all around Newcastle and Sunderland, so most places are fairly well connected. If in doubt, give us a shout and we can try to advise. The basic rule of thumb, though, is that anything north of the river will be easier. For reference, the closest metro to the venue is Central Station.