there are only 3 flaps (2 rear and 1 front) in that listing, but if you're after the embossed rear ones you can use them and either try to sell the one front flap on or disregard it
Actually...I hate Silverlake <_< ...well...it's not as good as it could be
I tend to go to Harris' in Nutbourne
...all you need is a hi-vis (supplied at the door) and an adjustable spanner LOL
infact there are 2 K11's at Harris' with the embossed mudflaps but...West sussex is quite a way away from Ayrshire