You can compare prices on this website:
https://www.volvopartshop.com/exterior-655-c.asp
It shows RRP but not certain if that is with or without VAT.
If you want a fitted price look up one of the last new car pricelists for your car as mudflaps, along with towbars, etc were dealer fit prices and usually consistant whether you bought them when car was new, or added later.
Eg here:
https://assets.volvocars.com/en/~/me...t.pdf?la=en-gb
£150 fitted front and back