Hi, I think you will find the straight part of your awning rail is nearer 2.3m in length. As regards awning on a budget, then if you like the more traditional style ridged awning then you would not go wrong with something like a Soplair. One for a Triton [will not fit] is on e-bay at present. You should be able to pick one up for around £200 in good condition. It will have either steel [strong but a bit heavy] or fibreglass [light but a bit bendy] poles. You can take the sides or front out to use as a big canopy if the weather turns hot.
You will see several AL or similar porch awnings up for sale at the moment. These may look good but are small and take the same amount of work to put up.
A campervan type drive away may be your thing and should also be considered as prices on these are low. They do however have some compromises.

Colin

Normally it's the straight bit that is important. Some Eriba specific awnings do have a triangular fillet/built in allowance at the ends and can go a few centimetres into the curve because of this tailored fit. If you bought a drive-away you would be wise not to exceed 2.4/ 2.5m
As an example, if you were looking for a sun canopy then a 2.5m Isabella would be a perfect fit as this is the actual fabric length. On a Fiamma Caravantore you would have to be a 2.25m as the extra length of the bag on a 2.50m would eat into the curve.

Colin

Thanks David. Don't forget to take lots of photos for the forum members.
I've just noticed you have an Audi A3 diesel. I swapped to the A3 petrol a coupe of months ago and was pleased at how well it pulls. Managed 35mpg pulling a Triton. I expect you should be getting near 40mpg towing your Familia. I'd be interested to hear what figures you get.

Colin