Jessops photo stores stock the Ilford range of 120 films.
For normal everyday use in a box camera, you should probably choose HP5 film. This is a conventional black-&-white film which needs to be processed in chemicals specifically intended for b&w films. (Remember that b&w processing is a specialist job these days and can cost quite a bit more than colour processing).
Alternatively, you could opt for XP2 film. This is a 'chromogenic' film which produces black and white pictures but is processed with colour chemicals (which keeps the processing costs down). In theory any photo lab can handle this film but I'd prefer to take it to somewhere like Jessops (where they know what they're doing).
I'd suggest HP5 for the best quality images but XP2 for more economical processing. Both films cost �2.19 each from Jessops (with discounts available for packs of 10).
Find your nearest store here:
http://www.jessops.com/Services/Storefinder/de fault.aspx
or order online:
http://www.jessops.com
Chris