I took my old strip light out and didnt properly look at lay out,now ready to put new light up it has 2 brown wires, 2 copper and 2 blue wires. Would all these go into same terminal on new light fitting
Because it's not the only thing on the circuit.
Take pictures before you remove any wires, (too late for you now, evidently) as wires might not be connected the way you might assume. i.e. when power comes in to a light, and then a "switch loop" switches the light, wires are NOT all connected same color to same color, and folks who blindly do that have troubles.
If the wires are all matched by color before you start, you probably have more than one light on the same switch, and it's a connection to another light.
In any case, it is virtually always the case that you hook them up the same way it was before if it was working before.
If it's just the one light, with the circuit breaker for the circuit off (hopefully that's obvious) use a multimeter to check for continuity between the blue and brown in each cable, to see if one of the cables has continuity that changes when the switch (NOT the breaker) is operated.
You got lucky, this is a spur with only a single mains, a single light & a single switch cable. This is by far the easiest to diagnose.
They do not all go in the same terminal. Some do, some don't.
First, you have to figure out which cable goes where.
One cable is the 'live' from the fuse box/circuit breaker. The other goes to the switch.
If you have a continuity tester, then find which set goes to the switch by testing [with the mains off] connection between brown & blue on each cable. The switch one way [on, of course] should show continuity, the other way no continuity.
Once you've established which is the switched live you can wire the other [mains] cable to the mains input on the rose - a rose will have 4 terminals, Earth, Live, Neutral & Switched Live.
Your mains cable goes to Earth, Live & Neutral [bare, brown & blue]
Your switch wires go into the same Earth and Live terminals as your mains cable - but then the Blue goes to the fourth terminal - the switch.
The existing wiring in the new rose will already have a wire to the switch & neutral terminals. Leave these in place.
Note: to be fully compliant with building regs, the switch cable should be brown, brown, green [bare], not brown, blue, green, which would make it easy to identify. In practise no-one ever does this, they just use the same cable as for the mains circuit, leaving you to figure this out for yourself if you forget to take photos.
See - http://www.lightwiring.co.uk/multi-point-radial-lighting-circuit-new-cable-colours/
Your wiring is 'Room 3', the last in the line; which makes it the second wiring diagram below.