The Spinflo sink and drainer in the picture below is 610*355mm and an almost exact fit in the Centaur sink space. Just a little trimming with an angle grinder is required to make it fit. Remove the original fibreglass sink by cutting round the edges using a Dremel with a right angled attachment.
Added - For those not used to working with stainless steel, an angle grinder with a thin (1mm) disc is needed otherwise the steel will heat up and 'blue'. To drill the hole for the taps a cobalt drill bit (very hard) is needed and with a cobalt holesaw if needed. Drill slowly with plenty of oil to lubricate and cool. My normal drills went blunt before I'd made much impression. The other thing to note is that the fibreglass recess that you are fitting the new sink into is not totally square. Careful measurement or a template should be used before attacking the new sink. I'm now on my second sink so I hope this helps others not make the same mistakes as me!
The original sliding cupboard doors above the sink have been replaced with full width top hung doors. A piano hinge along the top edge provides the hinge and a locking push button latch is fitted to ensure the doors stay shut in a seaway. The doors have stays so they can be left open and when open the whole of the cupboard is conveniently accessible.
The cupboards are lined with alluminium reflective loft insulating foil from B&Q which is cheap and provides a wipe clean surface.
Spinflo Sinks avilable from here Rainbow Conversions