Builders have done a botched job. Where do I stand legally?

I had my house refurbished just over a year ago... At the time I had problems with leaking appliances eg washer and also the bathroom that they installed due to poor workmanship. I own a share of the freehold and the appliances leaked to the downstairs flat. Not good. Anyway they fixed the leaks and everything seemed ok. The sealant on the shower failed as a result of it not being shower sealant, was roof sealant. Anyway it leaked again. Downstairs had to take down their ceiling and I then saw the extent of damage caused my the leak, rotting joists etc etc. Anyway I got a professional in and he said it was poor workmanship and fixed it all. I then got him to look at the kitchen stuff and that required work too eg pipes were sealed with gaffer tape etc. Anyway have spent over �500 sorting it out. And myself and downstairs have had to issue a claim for the damage downstairs, something that I feel we shouldnt have to. Anyway I employed a interior design firm to carry out the work on my house and they sub contracted to other builders. Do I legally have any sort of come back for the expenses I have incurred? I haven't contacted the firm yet as I wanted to get advice first. I have kept all emails, invoices etc also the plumber that did the work said he would go on record saying it was a botch job. Any help you can offer would be greatly received!!