I know Yatton well. Used to see a girl out that way a few years ago lol! Are you on Facebook? There's an IS200 group with a few members from here and other Japanese owners clubs. It's sort of a mini owners club and there's a meet down Cheddar second week of next month. I'm thinking of going if I'm not working.
I used Lexus Bristol, they were £90 more than that Toyota specialist in Warmly IIRC for the 100k service but I'll be honest I enjoyed the customer service, the free coffee and pastries and they put skysports news on the TV :)
Lexus also changed any bulb in my car that needed changing, exterior and interior without being charged, car came back fully valeted inside and out and they balanced all 4 wheels for no extra charge.
My car also came with an ancient mobile phone system. Had its own wires and fuses straight to the battery, and like you say got in the way of the passenger seat. The cradle was bolted on as well. I ripped it all out as soon as I could.