The Motebecane with Sora looks like a pretty good deal - a lot of people start out with Sora, it's good, lasts really well and is easy to use. You get Carbon forks with that bike which is good as well. I think most entry level bikes are pretty well about the same value. Sora is 8 speed whereas Tiagra 9 speed, and the new 105 and up is 10 speed.
Tiagra is also good, from this level you get the extra shifting lever behind the big lever, whereas on Sora it's a button you push on the side, but it works well. It's a bit hard to explain, have a look at some bikes at the shop.
The Giant OCR3 has always been popular - some people at my club race on those and are very happy with them, that's a Sora equipped bike.
I also have a problem with high blood pressure, and was one of the reasons I got back into cycling - it has done wonders for me, it took a while, but along with a good diet and regular riding. Also, since joing a club my fitness has improved very quickly - you tend to push a little harder than you normally would on your own.
clipless pedals and shoes are excellent and I highly recommend them - they take a little getting used to but are well worth it. It is probably best to ask at the shop for a demo on how they work.
also, make sure you get the bike store to fit you to the right size bike - that is important.
Good luck on your adventure of finding a bike, make it fun.