Normal Marathon on the front and Marathon Plus on the back, because getting the rear wheel off is a complete pain. Probably also good to ask the shop if it came with cheapo inner tubes and if so replace them with Schwalbes or similar – the marginal difference in puncture resistance is tiny at best but I reckon it’s worth it. A puncture out on the trail is one thing, but getting one while rushing for the train home is a different matter altogether 🙂
I think some still come with pumps but my straight handlebar 2-speed Ti one didn’t when I bought it about 5 years ago (the previous ones did). I carry a small pump in my bag, along with the Brompton toolkit and a couple of patches just in case. On the rare occasions I do get a puncture I have always been able to find a shop to fix it for me, but I like to have the option to do it myself. A small packet of wet wipes, and a pair of latex gloves, is also well worth carrying – my most irritating Brompton problem was when the wind blew a small plastic bag, the kind that you put fruit into in a supermarket, into my rear wheel and it got jammed around the sprocket and shifter. It was a complete pain to pull out and made a terrible mess, but I was at least able to keep going and clean up a bit.
I always use the front bag. The Brompton is designed to take a bag there, and it rides better with a bit of weight on the front. It attaches to the frame rather than the bars so doesn’t get in the way of the steering at all.
And don’t carry a lock – Bromptons are incredibly popular with thieves so it’s best not to be tempted to lock it up outside anywhere. I know people who carry a small cable lock for use on the train but I’ve never bothered, I just sit where I can keep an eye on it – mine is about a metre behind me right now….