Would have been £12.98 Parcelforce 48, or £16.95 First class signed for medium parcel up to 5kg.
RMSD costs more because it has £500 compensation cover, PF48 has £100 cover, RM signed for £50 cover, It's the cover that costs money.
If you use a courier you will probably only have £20 cover
You get what you pay for
Oh & if you use RM or PF via an on-line courier where it's cheaper you get far less cover value !
read the small print