I don't know where you are going to find a shop in Nimes to buy alcool a bruler. It depends when you get into Nimes centre from the airport to search. I arrived early afternoon bought my ticket to La Bastide Puylaurent on the1700 hrs train. That arrived fairly late at about 19.30.
I stayed the night at a gite d'etape, L'etoile,[English spoken] which is still advertised, its 40 euros BB & evening meal[ thats all they do] staying in the dormitory. With the meals thrown in it was good value. There was a bakery and grocers shop to get food for lunch for the walk to Le Bleymard.
At Le Bleymard there is the 8 to 8 supermarket near the campsite[ where I bought my camping gaz]. There was also a bakers just off route out of the town to buy something for lunch.
There were shops on the north bank in Le Pont de Montvert and a bakery over the bridge on the road to the campsite
At Florac there was a Champion supermarket on the way into town from Pont De Tarn.
Things change because I'm talking 5 years ago but on this section of your walk you are worrying unduly about shopping for food.
I think the problem is being able to find Meths or Gas don't forget you are offroad.
S'etonner, what are you going to shop for? There do not seem to be many shops around the central area of Nimes. There is a Decathlon on an outer trading estate where you should be able to buy gas cartridges. You'd have to find out which bus to ttake you there and back. Buses in Nimes had a flat fare of 1 euro per journey when I was there.
The Huit a Huit supermarket in Le Bleymard sells camping gaz cartridges if you have a stove that fits or adapter.
S'etonner I have not received any message. Its 5 years ago when I did this bit of a walk having done the whole route the year before so things could have changed.
I flew with Ryanair to Nimes we arrived around lunch time. There was a bus to catch to take you to the centre of Nimes just opposite the railway station. You cannot book local trains in advance on the internet so you've got to get your ticket at the counter. My advice is do this as quickly as possible because they seem to be notoriously slow and there's always some infuriating woman asking loads of questions while you fume in a queue behind.
You can look up train times on the SNCF ter website for Languedoc-Rousillon I've just done so for 1st July. There appear to be 2 trains in the afternoon one at 14.18 and the other at 17.00. It takes 2hrs 11min to La Bastide Puylaurent. For some reason the ter website calls it La Bastide St Laurent. I think I must have caught the 17.00 hrs train because it was late when I got there.
I did what you propose to do in May 2008. I flew Ryanair to Nimes in the morning and caught the train to La Bastide Puylaurent stayed the night there at a Gite d'Etape as the train arrived at about 7pm. [It was too late to walk to the campsite] Following day walked to Le Bleymard where there is a nice campsite and little Huit a Huit smarket close by. From Le Bleymard its a steady climb over Mont Lozere to Le Pont de Montvert where there is a campsite and shops. I stayed at the municipal gite d'etape there[which incorporates the museum] because weather was not so good, and at 12 euros was not much dearer than campsite. From le Pont de Montvert if the weather is fine its a splendid walk up to the Col du Sapet and along the ridge, you descend to Bedoues and on to Florac. There are campsites at Bedoues and at Pont du Tarn just before you get into Florac.
I walked on to St Jean du Gard so you are on your own from there. Early july shouldn't be too crowded but GR70 is popular with the French.