Hello,
I have never and doubt I will ever give the driver a tip - the are paid by Tesco to deliver and we pay Tesco. Some of them are very nice guys, but if I was to go around tipping everyone who was nice that just did their job, guess who'd be all out of money pretty quickly ?
As for the shortage of availability that haroldsxxx has asked about, perhaps the Tesco delivery location has now got a lot more customers than it used to have and needs to take on more vehicles and drivers, or change some of their current drivers shifts around ? .. phone Tesco and put a bit of pressure on them regarding the lack of availability of drivers at your preferred times would be my suggestion.