Google Maps satellite view: https://maps.google.co.uk/maps?q=pai...rbour&t=h&z=19
I'd have thought Paignton would be a bit tight at the top of the slip with an 8m boat. I'm relying on memories of launching an SR4 there in 2008, though, so it may be bigger than I remember. And I have no experience of 8m boats.
It's reasonably wide and not especially steep, but slipway dries out, and it's fairly sticky beyond that if I remember rightly.
Parking-wise, you can go round to the multi-storey behind the sailing club, or search for a space on Cliff Road or nearby. That's what we did when I was last there, not being keen to pay for a whole day's parking every day for a week. On foot, you can cut through the multi-storey and come out behind the sailing club, so you don't have to walk all the way around and down the hill to the harbour.
Further up the coast again, Torquay has a marina. I did leave the Searider there during that week, but we were being ferried back to Paignton by the sailing club, so I know nothing about it other than: it's a marina; it has fuel; it has a slipway you can launch a Nationals fleet of Cadet dinghies off (I have no idea whether or not that's a public slip).