I mean, if Germany was united in 1990 it could easily have butterflies for Britain. It had joined the ERM at a high exchange rate to the Deutschemark, and was obliged to shadow the Bundesbank's monetary policy. IOTL this was difficult but paid dividends - Kinnock brought Britain into the Euro with the rest of the EC and spearheaded the transition into a low-inflation, social market economy like Germany's. However, his lot would be made a lot more difficult if he had to shadow a Bundesbank saddled with reviving East Germany. It might even force an exit from the ERM, which would probably erode the wafer-thin majority he won in 1992 and prompt an election less than a year later - one the Tories could easily win. That means you have PM Heseltine come the War in Sudan, which knowing his OTL views is probably a bad sign.
Also, I imagine that a united Germany in 1990 would probably open the other Warsaw Pact states up to NATO and EC membership fairly quickly. As mentioned above, you also wouldn't have the Prussian poach to upset Poland. Since the Commonwealth of Independent States was a house of cards from the start, the allure of the West on their doorstep could very well prevent the reconsolidation of Russian influence in Eastern Europe, and lead to an EC that stretches possibly all the way to Ukraine (and "Belarus", which existed for about 5 seconds in the early '90s).
