I have a Diamond Back MTB, like this one
; the frame was built to order, as off-the-peg frame sizes were too small for me.
It is not a hybrid, although I modified it as such; fitted it with "slick" tyres which are more suited for road use than the "knobblies" it came with.
It was new in '95 and is still going strong, £450 notes well-spent.
I agree with SHJ
; Evans Cycles are good, as are Decathlon. I can't vouch for the quality of their in-house brand (b-Twin, IIRC).
Avoid Halfords. No offence Halfords, just my experience.
If you have a good independent cycle shop in your area, use them.
A really good one will take the time to measure you up for your machine.
As to spec - Shimano chainset/ brakes. Go for Cantilever brakes, or the V-Brake system. Disc brakes are, IMO, only for going down 80-degree slopes.
Wheels/hubs - Look for Weinmann rims/ hubs. Alloy of course.
For a seat, you can't go far wrong with Selle. (Mine is a Selle Royal Gel saddle, and is very comfortable.)
Suspension is a matter of choice. I prefer none. I seriously doubt you will feel the benefits of a machine so equipped for the use you describe.
Decathlon have a good selection of cycle wear, if that's your thing, including the spray-on Lycra. A helmet is essential
if you are riding along canal towpaths; hitting low-hanging branches hurts! (I know.)
Hope this helps.
Enjoy your new machine.