Here is the solution:
1. Clothing Store - C: 'Do you have this in an extra large?'
2. Hairdresser - D: 'Just a wash and blow-dry, please.'
3. Butcher's - L: 'A kilo of steak, please.'
4. Bakery - G: 'These are fresh from the oven.'
5. Pharmacy - I: 'I've come to pick up my prescription.'
6. Shoe Store - C: 'I take a size five, narrow.'
7. Optician's - X: 'Are you long or short-sighted?'
8. Post Office - E: 'I need to send this first class.'
9. Florist's - B: 'A dozen of those pink ones, please.'
10. Fishmonger's - F: 'They were caught fresh this morning.'
11. Newsagent's - A: 'Is this the July issue?'
12. Jewellery Store - H: 'Do you prefer gold or silver?'