Wear very well cut beige and grey clothes, occasionally a bit of white if you are feeling daring. Perhaps a bottle green jumper now and then if you are very BCBG (Sloaney).
Get your clothes altered after purchase so they actually fit you properly.
Spend about £80 on a bra and always wear the matching pants with it.
Wear Dim tights (which are quite fabulous, actually)
Spend a lot of time sniffing food at the market before you buy it.
Eschew milk in coffee unless it's breakfast time.
Eat about 3 times as many fruits and vegetables as the British, in both variety and type. Sniff and savour them a lot. Know which market stall to buy them at to get the best flavour.
Never snack or walk down the street eating. Non, non, non!
Again, if you are BCBG make sure your children wear Start Rite shoes and Le Petit Bateau pants and vests at all times (about £20 per pair of pants).
Increase the frequency of hairdresser visits by about 4x and never have split ends or grown out highlights.
Fret less about your home decor.
Give your kids watered down wine with Sunday lunch.