My impression is that a good frame builder would be able to replace dropouts and smooth out corrosion whilst trying to spray and blend paint job.
Don't think quite so simple - the good frame builder needs to have good experience with composite / Ti combinations or he might make a bodge. Bit like the time I dropped the ladder as a kid getting a ball off the roof and fixed it with wood glue. Luckily my dad was only 2 rungs up when it went...
A good Ti welder might not know enough about Composites and vice versa. The market for independent Ti / Composite combinations, outside of F1 / Moto GP type applications is pretty small. In fact someone like FTR who build Moto 2 bikes might be a good shout. I think they're based in the UK. Of course, they may not be interested, but may be able to point you in a good direction.
I'm not aware of anyone building Ti/Composite bicycle frames in the UK?
Not so much a six pack as a barrel!
1959 Carlton Continental 1982 Carlton Professional
1987 Peugeot Perthus Pro 753 1995 Colnago Superissimo
1995? Vernon Barker MTB 1993 Colnago MTB
2005 Colnago CT2 2012 Ribble Audax