Criminal convictions = strike off?

You might think so, but in my experience, it is not always the case.  Even when suspended sentences of imprisonment are imposed, as in a recent case, where my client had been convicted of a drink drive offence and assaulting a police officer.

Following detailed advice to my client over a number of months, we were able to negotiate an agreed sanction with the NMC, which meant that my client could continue to practise as a nurse - despite their initial fear that they would lose their registration. 

Your fitness to practice issue might look hopeless to you, but I see each case as a problem with a solution that just needs to be worked out.  It is always worth taking advice on what can be done; because usually something can be done!