Ok so i am in madrid,spain right now and have a bunch of midi controllers i aint using so i want to send them back to the uk so they can be sold,the problem is finding a place to ship them back at a good cost

i have a dhl just down the mainroad from me went in and they want 79euro to send a keyboard thats not worth more than 50,now there must be some way to ship back to england cheap,as i know sending from england only costs like 10 to spain i just dont no where to look,and still learning spanish is not helping my quest,so if anyone has any tips or places/websites that i can sort this would be great cheers