The distributor was about £290 including tax and the leads and coil were of course extra.  I shall be ordering a set of plugs on monday.   As far as I know they were options for 2 bolt or three bolt, but not sure whether you can fit without the adaptor if you need one. 
Take a look at the website. 
https://www.stromberg-97.com
it may answer your questions. 
Andrew