Shouldn't you have been offered your prescription back to take elsewhere to get your strips? If it is your normal chemist, why don't they keep a back up supply-mine does. With the qty of strips that type 1's and 2's need, I would have thought it should have been a priority.
I did a mystery shopper months ago on a Lloyds Chemist-and they didn't have the strips...when I wrote my report I did mention it that I thought it was imperitive that Lloyds being one of the biggest chemists should always have a supply of strips in stock.....
I would drop a line to their head office.
Did this recently with Ryvita, and got a lovely voucher in return....it was a genuine complaint and concern. Also notified Lidl's recently of a lovely young checkout girl who asked if I was ok at her till when I was there. I wrote to her head office and got a nice reply back (no voucher), nice to say thanks and nice to complain when genuine....and I think your complaint is reasonable and a genuine concern.