Manufacturers:  
Typhoon Sports Cars New owners of the (formerly Sylva/Meggt) Mojo, based near Peterborough
Sylva Autokits The Riot and Spectre, based in Lincolnshire
RAW The (formerly Sylva) Striker & Phoenix; Toyota 4AGE engine experts
Fury Sportscars The (formerly Sylva) Fury
Useful Sylva Resources:  
JPSC   Jeremy Phillips Sportscars Club - for all Sylva genre cars
Sylva Chat Friendly google groups chat list
Sylva Drivers Frappr Map Great way of finding out the location of other Sylva drivers
Useful Non-Sylva Resources:  
Westfield Sports Car Club Useful forums for non kit-specific queries, plus 'For Sale' section
Lotus 7 Club Forums Caterham forums with some info on Zetec engines and Weber carbs, plus 'For Sale' section.  Unfortunately only members can post to this forum, but it is still useful.
locostbuilders Lots of useful info, from a very resourceful group of builders!
Engines:  
zetecinside Useful source of Zetec-E & gearbox info  
fms-ford-spares Ford spares at reasonable prices  
Fensport Toyota engines and other parts  
Mojo Build Pages:  
Trevor Bennett's build Good pics & Trevor used an interesting paint system
Ed's build A Mojo SE build diary
Other Kit Car Pages:
Tim Hoverd's builds Including a Westfield, Dax, a racing Fury and now a racing Spectre
r1ot.com Riot SE build diary & forum courtesy of Richard Burgess
Scott Makin's build pics CBR1000 powered Riot
Mistrale An interesting homebuilt mid-engined 2 seater with a 1.25 Ford Zetec SE.