Silverline is a poor quality brand of cheap tools. I wouldn't have one as a gift. the style you are looking at, with a settable click-stop, is the right kind to get (they are also available with an indicating needle)
If you can't afford a top quality one like Britool or Snap-on, Draper are fairly cheap and reasonable. (you should also get a long guarantee). I have not had Halfords own brand but they might be OK.
you also need a deep-reach plug socket. If your torque wrench is a 1/2" drive, you may as well get a 1/2" socket. The length of extension you need (if any) will depend on how much your plugs are recessed. You want the minimum possible distance between the wrench head and the nut, as it will cause a bending diagonal leverage and you will have to try to hold it upright with your other hand. .
If you are starting to work on your car, can you afford to buy a 1/2" socket set? It works out much cheaper than buying then bit by bit, and you should get a sturdy case to keep them in. You might even get a second-hand set at a good price, but in this case make sure it is from a good brand and is complete. Unless badly abused, they only part that wears or goes wrong is the ratchet handle. there are plenty of youngsters who buy tools to mend their cars, but stop DIYing when they get older.
10mm sounds very small, are you sure this is the size of the hex nut on the plug? Not the size of the hole it screws into?
