Size 12 Narrow fit women's slippers in the UK
You can get great deals on large size shoes at Amazon with a bit of patience. There's usually a good choice up to size 10 UK. Their own Amazon Essentials range now goes up to size 11 UK, with fashionable styles at great prices. The women's shoes department goes right up to 14 UK, although many of the largest sizes will either be Chinese brands or unisex. There's free returns within the UK for most shoes sold/fulfilled by Amazon & if you've got Prime, you can even try before you buy.
UK shop in Hungerford, Berkshire also selling online and by phone. Shoes and boots available up to size 12 uk (46 eu), in narrow through to wide width fittings (B - 8E). Most shoes are available in half sizes and all are made in Europe.