Advice

Tenancy Types and Management

Please can you advise on what we should do in this case:
Have a tenant - no lease. Tenant borrowed our set of keys to flat in Dec and failed to return them. Tenant then went abroad. Whilst abroad, neighbours complained of foul smell coming from flat so tenant was advised that a locksmith would be brought in as we had no access to property. Advised tenant to collect new set of keys from estate agent (at time not handling property but helping us out as we were moving abroad and they were handling another of our properties). Tenant was also to pay to agent outstanding &due rent as well as sign lease as agreed verbally in Nov.
Tenant made contact with agent via phone, but failed to collect keys or pay rent. Tenant gained own access by arranging own locksmith. Tenant now 4 months in arrears. Tenant ignoring all corrospondence.
We want our rent and we want tenant to vacate property. Considering we have no lease, what are our options?
Your assistance/advice on the above would be most appreciated. Thank you.