Breach of leashold - Lodgers vs HMO

Tenancy Types and Management

Hi. I have a few B2L properties but this topic concerns my residential property. Back in 2021, I purchased a duplex apartment - two floors, 2 bedrooms with ensuites, 1 powder room, and a living room. The apartment is a leasehold in Southampton. I've done a lot of research online and I came to the conclusion that I could have lodgers on the lower floor of the apartment.

I've contacted my leaseholder and got a permit to convert the powder room into a proper bathroom and separate the huge living room to add one more bedroom. The work has been carried and everything works as expected. I've also added sinks in the bedrooms, and installed locks on the bedroom doors downstairs.

It's been 5 of us total living in the apartment (my partner + me on the upper floor), 3 lodgers in two bedrooms downstairs. We have lodger agreements signed with them.

I was just contacted by my management company that I am running an HMO and I am in breach of the lease. This comes out of the blue, I wasn't contacted at all regarding whether they're lodgers or tenants. I'm looking for advice:
1. What would you do in my situation?
2. Any good property law lawyers in Southampton you could recommend?