the toku restaurant in japan centre (http://www.japancentre.com/) by the piccadilly tube his pretty decent ramen. i had the buta-kimuchi ramen. the soup was not too salty, which was to my liking. i had a combination, which came with gyoza, which was also good.
don’t order much of anything else at toku though! my girlfriend ordered teriyaki chicken, and it was hard and dry. they must have re-heated something they made the previous night. none of the servers are japanese, and cannot speak a word of the language. as someone who has spent every summer of his childhood in japan, this is definitely not the place to introduce others to proper japanese food!
the food shop at japan centre, is another story. you can purchase all kinds of instant ramen, and the selection is quite good.