Originally Posted by prairie tuber
What is the condition of your existing tubeset? Is is there any possibility of repairing the existing set?
I reckon this could be your best route. Have a look at AndrewH's thread on the recovering and refurbishment of his tubes by Paul Tilley - If you PM Andrew he may tell you how much it cost him (I'd guess that it was around 1/3 the cost of new tubes)
As your boat is 1.3 metres smaller than Andrews (2.6 metres less tubing), you should be able to easily refurbish to the same standard and add new valves for less than the £1000 that you have saved up.
If you go ahead with the PVC tubes from the SIB you will:
1. Lose all the money you had in the SIB
2. Depreciate the value of your RIB