CML Distribution are the UK & Ireland distributor for Team Magic from what I hear. They will be able to give you list of local shops that sell the parts.
As for the shells, either the Protoform Lola shell, Serpent shells, Parma Lola or Sarik Porsche 962 are the best choices. There might be others that work but these are the best of the current crop
Protoform Lola shells are distributed by CML also.
The Serpent Shells can be got from Elite Models in Mansfield.
Not sure who deals the others though.