BT021's are still available.I bought a rear in February, they seem to be quite heavily discounted now, about £140 a pair.
When they were good, 021's were very good. But when they went off, they did so quickly and they could become quite unpleasant. But who cares? They are now three generations out of date. You wont get the same mileage, grip or handling that any modern ST tyre will give so your final cost per mile, even at discounted rates, will not be much better. Even at £140 a set, 021's will give 5000 reasonable miles at 2.8 pence per mile. £240 will get you T30 evo's which are good for 8500 miles or more with better grip so costing you 2.83 pence a mile.