"What sort of value would be placed on a full sheet of 200 stamps I ask because I have such a sheet (plate 33 cylinder 8). Having done some research I can not find a value for it other than as divided pairs"
Having checked my latest catalogue I can inform readers that this sheet 2 phosphor bars + Coated Paper/PVAD gum was printed from 20 8 1979 onwards.
If this sheet were to be split, (and I am not suggesting that is should be) this may be the best way to value it, but the true market value at the end of the day is what ever another collector is willing to pay for it.
Prices for cylinder blocks are (lower block of 6) £12.50 and (upper blocks of 8) £25.00). Each individual gutter pair ( another 6 ) are catalogued in the region of £1.50 gutter pair and £2.50 as a vertical se-tenant pair. Why this is different I do not know as the are both one of the same item. I suggest a happy medium of £ 2 per pair.
Individual stamps catalogued as singles are in the region of 40p each, but you would be hard pressed to get this amount as this issue is mainly collected in the formats above. I would value them at face or just above. Do the math, add a premium, say 5% or so for the sheet being whole and you have your answer.