Must be my lack of culinary skills Jim, they always taste like blotting paper to me!
Treecatcher (and you will be on the upper Exe), although its a small river you really do need chest waders. You will only fish one or two small spots in wellies and while thigh waders will cover a lot of it you will get wet getting to the best bits.
A 9 footer with a DT4 or 5 would be best. The tackle shop in Dulverton will sort you out with the right flies.
The grayling fishing is not prolific on the Exe compared with the better known grayling rivers (or even the Tone) so don't expect to get twenty or thirty in an afternoon
Andy