The two you have linked to are different.
For the Screwyfix one: Each set of 4 LED lights has a central driver (aka 'transformer'). So you will need to connect your existing LNE cables to the driver. The kit will include smaller cables that go from the driver to each light.
For the Toolystation ones, they are separate 230v LED lights that have the driver inside each light, so you need to connect the existing LNE cables to each light.
Look in the WIKI for "Wiring Lights in Parallel" in the lighting section.
The Wago connectors are one way of making the connections. But remember that you will need to put the connectors inside an enclosure (WAGO make suitable ones for this!)
hi mr T...
i found the junction box in the loft insulation for one of the existing lights wired up loop in and out
and the wiring is ...black and red/blue and brown...what colours would i choose for my extension cables??
cheers and thank again for being so helpful