All standard Westerlies came with painted decks. Teak decks would have been an expensive extra.
On the otherhand a 20+ year old teak deck is a potential big bill for replacement in the near future. I would be looking for a boat without a teak deck. Painted decks are much easier to keep in good condition than teak and have excellent grip.
Westerly teak decks of that era were made of a thin teak veneer on a plywood sub-base, glued on to the GRP deck. They wear quickly and look awful. Many have by now had the teak/ply removed and the deck simply painted, or perhaps covered with Treadmaster. If you look at an Oceanquest with an original teak deck, you should consider reducing any offer by £20K or so to cover the work which will inevitably be needed.