the list is potentially endless depending on circumstance. have just move myself recently and, for example, if you own somewhere you need to get an overseas landlord reference from the taxman and organise letting moving forwards, if you're in rented then you need to make sure that you're lease gets sorted at the correct time. You may need to think about shipping of furniture, you need a different P45 if you leaving your current job and emigrating and it's useful to get things like evidence of how many years no claims you have from your car insurance. You'll need passport photos in abundance, although these are better sorted out here, and if you get the chance to visit before coming out you'll realise that if you want to furnish your own place you'll need to buy tasteful things in the UK, export them and claim the tax back as the choice out here is somewhat "limited". Make sure you enrol on the frequent flyer programme of whomever you are flying with so that you don't kick yourself later. Ever educational document you've ever encountered may well need to be certified/stamped in many ways, so dig out what you have early and ask your Uni for anything you are missing well in advance so that it doesn't delay matters. There'll no doubt be countless other things, but everything is easily manageable so no need to stress (I managed to get it all organised in a couple of weeks so you have way longer to get your ducks in a row).

Good luck and look forward to seeing you both here in August (probably no need to pack the jumpers in hand luggage for that time of year!).