Hi Dickymint,
I live in Gosberton and I fish a little lake 2 mile from me at Donington, I don't know anything about the Grantham canal so can't help you with that.
Ours is only a small lake but the fishing is good, Roach, Rudd, Crucian, Tench, Carp, including Ghost, Mirror, common, Grass.
We lost a few fish in the summer and we thought we had lost our Bream but someone caught two the other day of different weights so we know at least we have two left, there is also a Sturgeon in there but no one has had it out yet.
It's 5 a day, or you can pay 50 in march for a year and you can fish it as much as you like.
It's behind a locked enclosure so we don't get any poachers.
Alan