What is the primary reason for wanting MTM?
Your budget of £600 could get you a suit of much higher quality if you looked at Ready to Wear. Going MTM is not going to guarantee a perfect fit or end result first time around. A lot of people only manage to dial in their fit/preferences after the second, third suit.
For £600 you could pick up something quite nice in the summer sales - look at Polo Ralph Lauren, Dunhill, Gieves & Hawkes, Hackett etc
P.S. avoid 'A Suit That...