Spoke to Royal Mail - the item has been delivered and the reference number I was given was for a completely different name and address so looks like the AliExpress company have tried to fleece me.
Latest - so basically the seller tried the same scam again and posted up a completely fictitious tracking number showing the parcel had been delivered in Cambridge. Now, I live in Peterborough not Cambridge but it is in Cambridgeshire. This 'evidence' also showed that the 'order' had been placed on 14 Aug whereas my actual order was on 16 Aug. Did AliExpress understand or care about any of this? Did they balls. They have sided with the 'seller'. I have initiated a chargeback against my debit card and will doubtless go around the houses with Barclays.