Cleaning tape heads

[andrewthezmore]

I've noticed that the last couple of tapes I've listened to are 
significantly less sharp sounding than previous ones. Please can 
someone recommend an easy cleaning option for me? I bought this 
tapedeck off ebay for a tenner and have never cleaned the mechanism in 
any way since I've had it - I've never cleaned a tapeplayer ever in 
fact, if they don't work properly I've generally replaced them with 
something equally cheap and cheerful. 

Cheers
Andrew