There is a pretty good iPhone app called size my bike, costs a couple of quid, input loads of measurements of your human form and it's not a million miles from my retuel fit - fact....
So good point DK but if you're dropping that amount of coin you won't be spending ??200 on a bike fit really, but you will be stuck with a few brands at the stealers preference as you quite rightly state. I.e, some LBS offer free or very discounted bike fitting using retuel when u spend north of 2k
iPhone app, measurements against manufacturer website, check for stock at LBS and test ride - Evans whilst not everyones cup of tea do stock a lot of TT bikes and do test rides and have a number of brands to try... You could do far worse