I'd used some in the same store the night before with no problems - and they let me use Helping Hand £5 vouchers and also the 100 point token

To be fair I accept that this was a tad 'lucky' as neither are supposed to be used. The 100 point token says it "Excludes Tesco Gift Cards and Visa branded cards." As has been observed previously different cashiers react to these cards and tokens in different ways. I will try the tokens at another store or with another cashier. It was the particular reference by the duty manager to an instruction today re a limit on 3V that I was most interested in. I will contact Head Office / Customer Services to check what they say