Ok, you did blow quite high, so that will likely put you in what's called the High Risk Offender (HRO) category, but it's still not the end of the world.
Someone else will be able to give you a more precise answer shortly, but if it is your first offence and there was no crash, no one else involved, no injuries then don't worry about going to prison.....it is highly highly unlikely.
You will be banned for maybe a couple of years, there is pretty much no way around that. But there is a course you can take that will knock 25% off your ban, and you must ask for this on your day in court if it is not offered to you.....you can't ask for it afterwards.
You will also receive a fine and possibly even a community order. And you will have some hoops to jump through with medicals before you get your licence back due to being HRO. Again, others here will be able to give you a better idea of what that entails rather than me.
There is a lot of advice on theee pages and as you will see there are people who have been in worse and better situations that have all shared there experiences which in turn has helped others. Have read through and I'm sure someone with better knowledge of HRO will give their wisdom soon.....don't panic though, you've made a mistake, you will be punished, but if no one was hurt and there was no damage and it's your first offence then you have far less to worry about than you maybe first thought