Changing Light fitting - Old Wiring
A caveat, I am a US building inspector but I after some reading I think I can help you.

It appears that your home uses the pre-2004 coloured wiring schema and your newly-bought pendant has the post-2004 schema.  Your current pendant has the post-2004 colour schema as well.  At this point it will be as easy as replacing blue with blue and brown with brown.  The protected ground/earth (yellow and green) needs to be attached to the copper block where there are other copper grounds.

The issue I can foresee with your new fixture is that there are multiple leads and cramming those all into the existing wiring block could possibly be difficult.  

I personally would go to my local hardware store and buy a half-metre of similarly coloured, single strand wire (blue and brown) of a similar or larger size and wire-nuts that can hold 8 strands of wire; ask your store clerk, they should be able to help you.  Cut the single strand wire down to a comfortable size that you can work with and still fit inside the fixture housing when you are done.  Strip off a couple centimeters of jacket on both ends of the single strand.  Remove the 2-3 cm of the wire jacket on the ends on the fixture, gather all the leads together along with one end of your single strand and use a wire-nut to bind them.  Then take the other end of the single stand and attach it to your wiring block.  Do the same thing for the other colour.  

Finally, I don't see how your fixture is going to be able to support its weight.   The current fixture is actually being supported by the wire that passes the weight to the plastic studs and then the plate.  The fixture base you are holding appears to be much larger and have a hole where a threaded rod might pass.  You probably also received another component that would replace the clear, plastic box plate that is there currently.  If so, it appears that the black and brass block might have to be removed.  If so, here in the US you can just use a wire-nut to splice the strands together (which I think is more self-explanatory then the ambiguous black block that everything is wired to), though it might not be code in the UK or your county/village.  Just black to blue, red to brown and bare copper to green/yellow.

As always, do the work with your mains switched off at the breaker, don't depend on the wall switch. If it appears to be too much confusion for you, hire a licensed and insured handyman and electrician and ask if you can watch so then you have seen it done.