Do not sell to 'Webuyanycar'. They will only offer you £50 for it if it needs repairs, which isnt right as thats less than scrap value. They should not be in business imo.
Your options are:
1. Break it - people always after certain parts: Body panels, doors, stereo, dashboard, seats, door trim, parcel shelf, bootlid,bonnet.....
Then scrap the shell (which you should get more than £50 for)
2. Car auction - if it is driveable? could you temporary disguise the problem? give the car a good valet then auction it if you can.
3. Fix it - just because the cost of repair is more than value of the car doesnt mean you can't fix it. Were you happy with the car before the problem occured? If so you should consider this option as you could fix it and the car could last for many more years. Remember its all about the usage value of the car.
Hope this helps