Window locks - which one please?

[ZebUK]

Recently moved into a new property and we've got three sash windows. The existing locks are very poor and while buying some window stops we thought we'd buy new locks at the same time but not sure which ones would be best?

We're trying to go for as cheap as possible without compromising safety.

[The Builder]

I guess these are vertical sliding sash windows Zeb?
These are cheap, but from a good manufacturer....

http://www.ironmonger...K108_Sash_Window_Lock