You basically have three options here. The first, and most drastic, is simply to `forfeit' (i.e. terminate) the lease by retaking possession. You don't need to provide any notice. You just wait till the property's empty, then go in and change the locks.
If you do this you can still sue the tenant for the rent due up to the date of forfeiture.
The tenant has a legal right to apply to the Court for `relief from forfeiture'. This is an application to the court asking for their lease back. It will usually be granted on the strict condition that the tenant pays all the rent arrears and also the landlord's legal costs. It sounds extremely unlikely that there's any risk of this.
The second option is to use CRAR - Commercial Rent Arrears Recovery. This involves instructing bailiffs, who are empowered to enter the premises and seize goods to the value of the rent. I'm not really a great fan of this, the biggest drawback being that the bailiffs have to give 14 days’ written notice to the tenant, which is more than enough time for the tenant to hide any goods that are worth something!
In your case there may well be no such goods anyway, and as you can't get blood out of a stone the CRAR may well be a waste of time and money.
The third option is to negotiate a termination of the lease (a `surrender') with the tenant. You could, for example, offer to accept half the rent arrears in return for their vacating immediately. Of course, they may have no money, so that even if they wanted to do a deal they would be unable to, but I would always advocate at least exploring this option.