Buggy (lightweight one for flight), sunshade if you use one, sling/baby carrier (for airport at other side as they often dont give buggies back until at the luggage carousel), nappies, wipes, clothes, usual washing powder (if baby has sensitive skin), bottles and formula and steriliser (can use cold water bags if need be) if bottle feeding, jars of baby food for flight and first couple of days (so you're not pureeing like a mad thing as soon as you arrive at destination), clothes, a couple of toys from home and normal bedding. Dont forget their toiletries, some calpol and calgel (in case teething occurs while away)and sunblock and sunhat.
Sounds a lot but actually not that bad (their stuff packs v small).
Take change of clothes for you, DH and baby on plane (DH once spent an hour in US immigration queue covered in dairylea smelling babysick - made us realise we should have packed him a change of clothes as well as DS), more nappies and wipes than you think you may need (for accidents/emergencies) and get formula/baby food for flight at airside boots (as they are still bit funny about fluids on flights - call ahead to reserve what you need).
Thanks so much - brilliant tips - so glad I asked - would never have thought of some of those!
I am quite nervous about travelling with my LO but at the same time really looking forward to getting away. Just getting away from the day to day stuff and hopefully having some quality time for the three of us.