[Jon]

I suspect you may be a little early, suggest you do a google on Donna Nook and the Lincolnchire Wildlife website will probably give you a better idea. I remember there was someone who puts out regular updates on the arrival of the seals.
It is as well to check before you go - I travelled from the west coast to the east coast in 2005 only to find I was a week early and had to make a return trip the following week!
Jon