Without a doubt the most difficult thing to do is buy shoes. I have tried it and have been thrown out of quite a few shoe shops. The dialogue usually follows as:
Shoer: Hello Madam can I help you.
Me: Yes. I'd like a pair of shoes.
Shoer: Any particular type.
Me: Well a pair of clowns shoes would be good.
Shoer: I'm sorry, but we don't sell clowns shoes.
Me (looking around): But, I see some shoes here that look like clowns shoes.
Shoer: No I'm sorry they're designer shoes and are quite expensive.
Me: Well how about all these people they're dressed like clowns surely they're here to buy some clown shoes too?
Shoer: I'm sorry, but we do not sell clown shoes and I will have to ask you to leave.
At this point I'm usually asked to leave the store.
Clown shoes are indeed difficult to buy.
I have also had no luck when buying train passenger shoes (technically known as trainers). I usually use the following technique:
Me: I'd like a pair of trainers please.
Shoer: Yes madam we have a fine selection of trainers any particular make?
Me: Yes, I'd like British Rail trainers please.
Shoer: Ok, well most people tend to wear these green ones. Perhaps you'd like to try a pair of those?
Me: Yes indeed do you have them in my size?
Shoer: What size is that?
Me: I'm not sure.
Shoer: What size shoes are you wearing?
Me: I'm afraid I don't know. They're not my shoes they belong to a friend.
Shoer: Well do you know the size shoe your friend wears?
Me: Certainly not! I don't ask personal questions like that.
Shoer: Perhaps we can measure your feet then.
Me: I'm afraid that's difficult to do as I'm not allowed to take my shoes off in public.
Shoer: Right well if you could lift up your foot perhaps we could get a pair roughly the same size?
Me: That's a good idea. But, could you get them a bit bigger?
Me: Well, these ones are a bit small for me.
Shoer: Any idea how small?
Me: They seem to be uncomfortably small for me. Can you find a pair that's comfortably larger.
Shoer: I'm sorry, but we're all out of comfortably larger shoes perhaps you could try Bond Street they sell comfortably larger shoes there.
Indeed, I have had great difficulty in finding shoes in my size, colour and for all my needs. I have had to resort to creating my own shoes.
I have found that by creating a paper-mache of paper, glue and water in a bucket. And then putting my feet into the bucket I am able to make a resonably decent pair of shoes. By then sticking half-metre square pieces of carpet to the underside I have a comfortable surface on which to walk on. I usually wrap the shoes in tape to make them waterproof.
I have found that these shoes tend to wear better than those elsewhere and may be worthwhile trying out yourself.
Hope this helps