Hi Mate,
Those prices are good, I've worked in the kitychen industry for 30 years and when I worked in Installations (Up until July of last year) we would have paid the installers more than that and bear in mind that was when they were installing full kitchens - if it was just for those appliances (albeit they were mostly integrated fridges) we would have had to pay them a lot more.
Is the oven the same in terms power consumption as the previous one?
That being said you can do it yourself, but what people forget is that if it leaks after Currys fit it, the liability is with them.
I presume these costs also include them taking away the packaging etc.