Had a phone call this morning from an establishment in Pinner! Never been to Pinner in my life but someone has given my phone number but luckily wrong details obviously they just used a random number

What are the guidelines if someone else uses your details can the authorities insist you have to isolate if you're details are falsely given

It must be easy to do because it seems to me this is self policing when you give details

That sounds like one of 2 things to me -

Either a hoax/scam call, someone trying to get your name, DOB and link these to your phone, for a possible future scam whereby they try to access your phone and go online shopping. Hopefully it's not that.

Or.....

The Track & Trace centres are dotted around the UK but the Public Health England or similar agency who are actually making all the calls may be based in Pinner. No-one should ever receive a phone call from a business (e.g. pub, restaurant) directly.....if that pub has a problem with covid (staff-member or customer with a positive test) all they do is pass in all the contact numbers for other customers, staff, visitors etc who used the place over the same period. They pass these details to the PHE call centre who make the calls.

As you say, it could also be that some covidiot has given a false number when visiting a pub etc. PHE now need to contact that person to tell him to self-isolate but can't. Good karma might see to that person falling mildly ill now.