I lived in London last year on secondment from my Scottish base.
I had a massive burns supper for colleagues who were all v. curious. I'm a lazy cook and despite the protestations about how disgusting haggis was I decided I wasn't going to cook anything else but bought up loads of Veggie haggis (on the basis that anyone revolted by meat haggis would just eat veg). I made a massive vat of clapshot too (which is basically bashed neeps and tatties ready mixed up).
Despite only have 4 out of 16 pre dinner who were going to eat meat haggis and 12 who were vowing to only eat veggie we got through 2 meat haggi (can never decide what the plural of haggis is...) designed to feed 10 (ie enough haggis for 20 people) and had shed load of veggie left. The moral of this is that the English like haggis more than they think they will! Sod the scot who doesn't eat it!
I usually do smoked salmon and oatcakes for starters as my burns suppers are often so massive they are buffet style and soup requires you to have lots of bowls!
Cranachan for dessert as per the others and sometimes apple crumble too for those who don't like cream. Mackies ice cream is traditional.
I also had loads of tunnocks products - tea cakes/ caramel logs and Irn Bru.
We got everything we need from Waitrose (even Irn Bru) with no bother which surprised me in Central London.
You could be poncy and have a bit of whisky tasting comparing a peatie Island Malt, a lowland one and a highland one. Personally I'm a bit of a peat monster. Tasting sets are often available from the specialist retailers. You could go totally bonkers and also have scottish gin and tonics to start as we make fabulous gin (The Botanist being my favourite).
Oh and have a go at tablet it is fairly straightforward provided you don't get freaked out by bubbling sugar.
Loads of fab. kitchy textiles to decorate your table at Gillian Kyle (and no she isn't paying me to say that!)