There are companies that operate throughout Europe. I won't refer them on this forum. However, if you got to the MysteryShopForum, you ought to be able to find them.
Yes, there are some shops where the scenarios could use some upgrading. However, most of them actually do work out okay.
Buying small amounts of gas: For most of these shops, you pay at the pump (unless you are in Oregon or New Jersey, where it is illegal to pump your own gas) and the attendant never knows who much you personally spent on gas. Or, even if you do, you then ask to use the restroom (a required part of the shop) and it makes your cover: You didn't really need gas, you needed to use the restroom. However, you got a small amount of gas so that you could be a customer and,therefore, had the right to use the restroom. If you are only doing one gas station, you can always just fill up your tank. Most of us have to fill our tanks about once a week, anyhow, so it's not like we are spending more than we would otherwise.
It's been a while since I have done these phone shops. They are pretty quick and easy, unless you arrive at a time when the store is busy -in which case you might have to wait 20-30 minutes to be helped. Are they worth the time? That question is different for everybody. I live in an area where the cost of living is very high and minimum wage is $15/hr. The only time I pick these up any more is if I am already at the location and have a few minutes to kill. I also tend to focus on more involved shops that pay more. (I take very few shops that pay less than $50. Most of the shops I do are in the $70-$80 range.
I have never looked at the iSS spreadsheet... I have created my own for tracking shops, expenses, payments, etc. It's pretty simple to set up with Excel. Most of my shops are not through iSS, so I needed a document that would handle them. Were I just to us iSS, I'd likely be happy with what is offered online (the "assigned shops" tab and the "payments" tab).
Read and follow your guidelines carefully. Only sign up for a shop if you know you are going to do it. Your word and reliability is everything in this business.
It's the end of the year. Many companies want to have all their shops done before the holidays so that they can take time off and transition into next year - which could mean different clients, types of shops, etc. This is especially true with retail.
If you need to find more shops than what is on iSS, realize that there is a whole world of mystery shopping and the companies on iSS only represent a small fraction of what's available.
Some that I do take 10 minutes.... others can take 45 minutes. It all depends on what is involved in the evaluation.
Once you have submitted the shops, I believe you should be able to self-assign more - even while you wait for them to be approved.