Just to echo the comments from the others, it should take no more than 15 mins with hand luggage (probably less) to clear immigration and get back through security - especially if you are one of the first off the plane on arrival. I fly in and out of MUC most weeks and (unlike the terminal that LH use) the queues at the BA terminal are rarely more that a couple of minutes. I'll be there on Friday as well so will be trying to guess who LondonElite is...