if you ran into the currywurst museum in Berlin http://currywurstmuseum.com/en/ and repeated this i doubt very much you would make checkpoint charlie alive
I searched high and low for a UK supermarket selling this a few years ago and couldn't find it anywhere else. As far as I know, the German Deli is the only place in the UK you can get it, I just stock up when I have a day out in London, and it gives me an excuse to have a nose round Borough Market and a few pints in the Market Porter. They have a shop just round the corner from there. Agree about the extortionate delivery charge, and it's a bit pricey anyway at £3.95 a bottle, but it is the best ketchup ever and brings back many RAF memories. The shop sells loads of other German food and they have a Currywurst stall in the Market.