I've had a bit of a lead around the past day or 2. It's definitely very deep compared to other places I've fished, with an occasional clump of weed in places but I'm not sure 100ft is quite true, unless it's a hole I've not found yet. Someone I met on the bank yesterday said 60ft which may be more accurate.
There's definitely some shallower slopes and ledges around the edge and people have said they've had fish up to 22lb in the past couple of weeks, so maybe it's not as hard as I expect.
The difficulty is going to be making sure I'm not too deep.