Also, seems to me that in the UK, radios are on 35 mHZ, not 72 mHZ. Check to make sure that the crystals are correct for the reciever model. If you somehow got hold of the American based 72 mHZ crystals, the circuitry in a radio designed for 35 mHZ wouldn't work. The frequency determining components would be way off value. I don't happen to have one of my AMI mags with me, but 6EXA as listed in the Tower catalogue only shows the R127DF, so the R136F may be a European or UK only reciever, on a different frequency band. You should be able to find a UK based web site for Futaba for advise, or a UK telephone number.
If the system didn't work out of the box after charging up the batteries as recommended in their instructions, sounds like a return under warranty is suggested.
I think only the American FCC refuses to allow the free changing of transmitter crystals unless you have the proper commercial liscense and the training and equipment to ensure that the resulting output waveform meets specs. Maybe because of the narrow band separation?