Changing my window locks - any disadvantages I've not thought of?

[GrendelsMum]

I'm not sure if this is a property question or not, but here goes.

To give a bit of context, our house is a 17th century timber-framed farmhouse suffering from a bad case of the 1960s. I'm currently trying to make it look pretty.

Among other jobs, I'm removing the 1960s window fittings and replacing them with cast iron fittings.

All the windows currently have window locks on - a mix the large sort that screw onto the side of the window like this

www.locksonline.co.uk/acatalog/Chubb_8K102_Window_Lock_.html

and this sort

www.locksonline.co.uk/acatalog/Era_828_Locking_Window_Catch.html

To get the aesthetics, I'm keen to replace the locks with the sort that screw through the window stay, like this:

www.locksonline.co.uk/acatalog/Era_820_Staylock.html

Is there any problem I don't know about with doing that? e.g. less safe, insurers don't like them, etc, etc?

Also, a lot of the small windows have locks on, when I can't see that opening that window would actually do you much good. Do these really need locks on? Do burglars have cunning ways of getting through small windows?

I can imagine I may need to talk to the insurers, but I don't think we specified whether we have locks or not at the moment.