Sounds normal for an MOT, that they allow you to come back for free. You'd have to ask them how much time they give as it probably varies.
If you're interested in maintaining your own bike then it's definitely worth it. It takes 100% of the worry out of an MOT. You can pretty much take a 5 minute glance at a bike and you'll know if it will or won't pass. You can see everything and there isn't a massive list like on a car. It'll also be much safer than just relying on the MOT saying your bike is safe. Leaky rear brake calipers for example (something you would have noticed when cleaning or whatever if you learn about the bike & maintain it yourself) could have got interesting for you if the fluid found it's way onto the disc.
If you're interested in maintaining your own bike then it's definitely worth it. It takes 100% of the worry out of an MOT. You can pretty much take a 5 minute glance at a bike and you'll know if it will or won't pass. You can see everything and there isn't a massive list like on a car. It'll also be much safer than just relying on the MOT saying your bike is safe. Leaky rear brake calipers for example (something you would have noticed when cleaning or whatever if you learn about the bike & maintain it yourself) could have got interesting for you if the fluid found it's way onto the disc.