Oh lor.. Haven't we been here before? You'll probably get as many opinions as there are TM members Howard. For me a Plus 4 was very comfy on our run to Caramulo last year and I managed to keep my trousers dry! But it depends on your reference point, against a Caterham its a luxury ride but compared to almost every modern car on the road it's a bone shaker.
I'd hire one as Steve says but make it at least a week and drive it lots. A couple of days isn't enough for the novelty to wear off.
Wish you luck in your search, maybe go classic for a while? No gizmos to worry about, zero RFL and hopefully no depreciation.
