Tenants requesting eviction

Rent Arrears

Our tenants have persistently been late in paying their rent over the last year. They started the tenancy i June 2007. Relationship problems meant that the husband left before Christmas. We allowed the tenancy to roll on without changing the tenancy agreement, but husband wife and adult daughter are all named on the agreement, although only the husband signed it. We have discovered we cant find our copy of the agreement. The two remaining tenants owe 3 months rent, coming up to 4 months at the begininng of July. We have kept copies of remiders we have sent. They have been to citizens advice and asked that we evict them now. We believe they want a council house. We have a meeting on Sunday and have filled in Section 8 citing just the wife and daughter as tenants.
Any pitfalls we should be aware of? Is there a problem if we dont have a copy of the agreement. We do have their signature on an inventory which also mentions keys and meter reading on arrival. We also have the DPS informatiion with a record of their names and deposits at the start of the tenancy.
And finally...how do we get our money back.as well as our house?
And finally..anything we should or should not do or say at our meeting? Shopuld we ask for a signature when we hand over the section 8 form?