.......There are other major tuners, Emerald + KMaps come to mind,...)
Emerald only offer a stand alone system which requires some rewiring and potentially some new sensors. IIRC you are looking at around £600 to get started. However the owner can do their own mapping.
KMaps are similar to SAWS in that they remap the O/E ECU. They offer a postal or "at a show/meet" service with a generic map based on any alterations you have made or offer a full service at their rolling road near Silverstone. They don't offer any self tune option.
I was planning on sticking with my MEMS 2.0J but have considered swapping my mk1 VVC to MEMS 3 now that SAWS offer this option.