Can I sue my cowboy builder? (UK)?

[rene_pierin]

On 28th July 2008, I was injured by a piece of wood with a nail through it in the garden of my property, which currently being renovated. The nail went straight through my foot. The wood was left lying around by the builder who had been removing batons from the roof. I bled profusely but had to transport myself to hospital as my partner was at work. At hospital I was cleaned up and vaccinated appropriately, but was unable to complete any work on my property for several days. I can forward photographs if required.
 
With regards to the above renovation of a property, on 4th November 2008 I received an email from the building inspector, regarding a site visit to inspect the work to the roof. His comments included: "In general some of the workmanship and cuts involved in the roof work was of a poor standard and these issues should be checked to determine whether they will impact on the long term stability of the roof." I can forward the entire email if you require.
 
Following extensive calculations and engineering planning I was able to get the builder (Chris) to return to correct the most critical instabilities in the roof. However, this was after the roof was failed by the inspector. It took several weeks to arrange for him to complete the work.
 
At present Chris has not completed all work he agreed to do, despite the original verbally agreed and witnessed deadline being the end of July 2008. This has persistently been pushed back and new deadlines agreed. He has consistently failed to turn up when he stated he would, and weeks have gone by without any work taking place.
 
The property was purchased as a rental investment, and I have had to turn potential tenants away as the work has not been completed as promised, at a cost of £450-500 per week.
 
There are several areas of workmanship that are substandard in the property, these include leaks appearing in kitchen ceiling, poor roof construction, poor quality and fitting of facias and soffits, door lintels not fitted to standard, kitchen worktop cut out for hob not square with cooker hood etc. This list is not exhaustive and more detail and photographs can be provided if necessary. We have since employed a new builder (Phil), and the difference in quality and reliability has only served to highlight the original builders inadequacies.
 
There were also gaps in Chris's knowledge relating to HMO's and building regulations which have caused me to change my plans as the work had reached such a point in would not have been financially viable to make the changes necessary. Originally the house would have been converted from a dwelling house to an 8 bedroom HMO, I have had to compromise and make it 6 bedrooms only, again, at significant financial loss to myself.
 
What do you recommend that I do at this point? Is there anything I can do? Should we allow Chris to continue working? (He said all jobs would be finished by the end of this week but he has failed to turn up for the last 2 days). He will undoubtedly demand to be paid the final installment of his fee, a total of £2370, this included the amount he added for correcting his work, which caused the inspector to fail the roof. I have already paid for partitions to be built, these were so shoddy Phil and the plasterer had to remove and rebuild them, at extra cost to myself. If Chris finishes work this week should I pay him? Every time he has asked for money he has been paid promptly and in full (again I have proof of this, handwritten by Chris himself), by the method he chose (mainly cash or bank transfer).