It would seem that both businesses and the public are confused about the use in the UK of old and new £1 coins, £5 notes and £10 notes.
The new 12-sided £1 coin became legal tender on the 28th March 2017. As from 15th October 2017 the old coin will cease to be legal tender. From that date businesses and shops will no longer be obliged to accept the old £1 coins. Old £1 coins can be exchanged for a new £1 coin at High Street banks
The new £5 note became legal tender as from the 13th September 2017. As from the 5th of May 2017 the old £5 note ceased to be legal tender and therefore should be traded by either businesses or the public. Old £5 notes can be exchanged for a new £5 notes at High Street banks
The new £10 note became legal tender as from the 14th of September 2017. The exact date the old £10 note will cease to be legal tender has not yet been set by the Bank of England but it will be in the spring of 2018 and 3 months’ notice will be given. Until then the old and new £10 notes can continue to be used although High Street banks will exchange the old £10 notes if requested.