I've wanted a racer so I can hit the country roads and do some serious cycling. Recently I've been thinking about touring so I can practice French I have been learning for the past years and touring around France in the summer seems the perfect French lesson for me!
I think you need to go back to square one and settle on two things;
1. What is the primary purpose of the bike you will buy?
2. What is your budget, including any costs to adjust/upgrade/repair the bike for it to meet this primary purpose?
Do you have camping gear already or is that a necessary addition to your budget? Don't forget to estimate the cost of racks and panniers also.
I can understand the desire to get a bike that will do everything, but I think that "Touring" and "Racing" are far apart on the bicycle scale. The more "racer" it is, the less suitable for touring and vice versa.
Even if you decide that one bike will do both jobs, you may want to consider different set-ups for the bike depending on it's use.
At the very least you will want different tyres for racing as opposed to touring. Maybe even different wheels (dynohub for touring?).
What exactly do you mean by "serious cycling"? Do you mean races? Do you mean group rides? Or just heading off on your own? Is distance and speed the priority or is it more getting away from it all and enjoying a different landscape?
Also, is there a reason why you are looking at older bikes? Availability of spares and the technical knowledge is declining all the time. Not saying it can't be done, just a bit more difficult depending on your skills and knowledge.
The most important factors for a touring bike (in my opinion) are comfort/fit and stability carrying a load. It has to be comfortable for long days and it has to be able to carry your baggage. When considering a non touring bike for touring, a critical thing to look at is the length of the chainstays to make sure your feet have clearance on the pedals and do not hit any panniers. Therefore any "racing" bike that meets those criteria should be viable. I exclude gearing because that can be changed in almost all cases.
After that, it is up to yourself. Anything with "old" technology will require either the input from a bike shop or your own self acquiring skills for maintenance, repairs and upgrading. Anything with more common technology will be easier to handle yourself.
One way of using a "racing" bike to tour is to consider a trailer. Not cheap, but a way to carry gear for camping/touring.
If you want the most flexible and most economic way of creating a multi-use bike consider converting an old MTB. Old steel frame, good gearing, typically with mounts for racks etc. If you want you can add drop bars. (Not straightforward, but doable). Have a look on any second hand site and you'll see suitable bikes for 30 or 40 quid. Building one up will enhance your knowledge and skills and allow you to create a bike that will do what you want it to do. The low cost means that you can spend your budget on the components/gear to allow you do what you want.
Just bear in mind, when it comes to touring there are so many possibilities in terms of locations, distances, surfaces, seasons, length of time. Also it is addictive! It is quite possible that once the bug takes hold of you that what you now consider to be "touring" will change extensively once you try it. A bike that is flexible will be more useful.
Whatever you decide, you can tour on any bike. Some will make the trip more enjoyable, others, less so, but France is fantastic for touring!
Enjoy!