The higher the numbers generally the better the quality of the GM bats and 606's are the mid-range for GM. The Halo is being discontinued so obviously it is going to be a bit cheaper but getting one for £47 sounds like a real bargain.
However you will only learn if it is worth that money when you actually use it.
thanks MattB for your reply.
I went ahead and bought the bat. I got the price further reduced by 10% because of some light marking/scracthes on the back. 11 grains(9 narrow & straight) ping is great already, doesnt require any knockin in, responds well better then my GM epic 808.