haha my dog knows when she hears my husband coming to get off our bed and into hers haha
I just had a bed delivered from John Lewis! Here it's king size, there it's a short queen size bed. Anyway, the delivery guy looked at me in horror when I said the dog thinks it's for him. There's gonna be a lot of negotiation when there is another human to share 'his' bed with. Though he likes her so that should help! I tell him to get in his dog bed but as soon as he thinks i'm asleep he creeps on.
Definitely possible to buy flat sheets here, and as others said we use duvet covers instead. Sorry we don't have a Target

For Homeware I guess I use combo of John Lewis, Ikea, Sainsburys, and Argos. Coop electrical too, and B & Q (like got lamps there). I tend to get sheets from John Lewis. They have good click and collect service if you happen to have a Waitrose nearby.