parcel2go have adopted a £3.99 under 2kg, but it's multiple with a one off £5 collection fee I think, so if you want a lot at once, and normally dropped off with DHL that might be the way to go. I have been considering, as I shelved the ebay selling for now, as ebay tell you not to buy from royal mail postage sellers at present, seriously affects end prices.
details here,
https://www.parcel2go.com/order-new.aspx?serviceid=156
Have used them for international and huge things like a Baja %B not been let down yet.