What legal powers does a (UK) person have without having full legal qualifications? I am interested as you can't represent someone in court without being a fully qualified solicitor/barrister (as far as I know), yet for "power of attorney" you can represent someone in their place but I don't know the limits to this. Is it different for someone in the process of training for a law qualification perhaps?
You can always (as far as I'm aware) act as a "litigant in person", which is the UK phrase for a person representing themself in court. Whether its wise or not depends on the case - because the procedural stuff can be heavy weather and lack of knowledge about legal writing and law can be a real detriment. Courts have instructions to bend over backwards to help litigants in person, but if your lack of knowhow wastes court time or causes another party to incur costs, those might be a problem on your plate.
The UK judiciary does a free PDF handbook, called a guide for litigants in person. Download it.
You can somewhat represent someone else in a manner of speaking. But not formally. For example,
you can write their case and letters, handle their correspondence etc, but they have to sign it and they remain responsible for its correctness.
in court, they can tell the court that you are better placed to discuss the legal points and they would like the court to talk to you instead of them, and the court has discretion to do so. But again, they clearly remain the litigant and the court at any time may deal with them directly, it's not a "right".
there are legal roles such as "MacKenzie Friends" but I don't think those are what you're after. (official guidance, eg see paragraphs 2-4 and 18-25)
There is no such thing as 'half a lawyer'; either you have the relevant qualification (such as being a trained barrister/solicitor-advocate to represent somebody in court) or you are not, in which case you have the same rights as any member of the public. Paralegals are in the second category: they can read documents and suggest a course of action (well, so can anyone on this website), but cannot act as your legal representative, nor charge for legal advice.
'Attorney' in Power of Attorney comes from the same root as 'legal attorney', but does not have the same meaning. If you hold Power of Attorney for your ailing mother, you can and in some cases must act on her behalf; for example, if the plumber fixes her washing machine, it is you who pays him. Similarly, if she appears in court you can appoint a solicitor to represent her; whether you can represent her yourself is too complex and fact-dependent to give an opinion on.