Tenants won't go and trying to agree outside of court

Possession - Section 8 and Section 21

I'm looking for any guidance with my sitauation. Deep breath...
My tenants are husband and wife with two teenege children and took my house on a shorthold tenancy agreement in 2007.
The first two years were largely ok, however,in the past 9 months have regularly failed to pay rent due. They now owe me nearly £4000 after many failed promises.
The monthly rent due is £700 per month

I have issed both a section 21 and section 8 notice. Due to long local court delays, the hearing is not until end of July.
(another 5 weeks !! )

The tenant seems to be 'playing the game' and now would appear that they have been down this road before.

They have requested me to cancel the hearing (clearly they don't want a CCJ against them ) and suggesting will pay me £150 per month towards the debt and will leave the property within 4 weeks - so before the court date. This is the carrot they are dangling at me...

They have also said that if i proceed with court hearing, they can extend there stay by dragging it out throgh court which could take another 6-8 weeks !! Cheek of it.

Also have said that the court will instruct the debt to be repaid based on family circumstances. Children etc £50 per month ring a bell with anyone ?

Finally, my question is....

If I agree with tenants to settle outside of court and they agree to move out within 4 weeks, then consequently fail to pay the £150 per month towards the debt, Can I still pursue them for the debt through section 8 even though I've cancelled the hearing?
Phew !!