Bude has all the things you ask for. I'd particularly recommend walking the cliff path from Tintagel Head to Trebarwith Strand. The cliffs are spectacular anyway, but slate quarrying has made them even more so. At one point there is a tall rock pinnacle that the quarrymen left standing as it was of poor quality and it remains like a Cornish version of the Old Man of Hoy. It's also worth a look at Delabole Slate Quarry, which is an impressive hole by any standards. I haven't been there for a few years, but it used to be possible to view it from quite a few public places without upsetting anyone, though tours do take place. Look out for the local traditional slate walling, with layers of stones alternately lying different ways - known as 'curzeyway' walls. they can be quite photogenic. Just inland from Trebarwith is Prince of Wales Quarry, where there is a restored engine house.
Sorry to go overboard with quarrying and industrial archaeology, but it's my thing!
Enjoy your trip,