I had much the same choices to make. It's heavy work that needs to be accurate. I got a reasonable quote from a contractor so I used them. It was done and dusted in a morning. A very good solid job and I specified concrete base panels to keep the wood off the ground. I'd nave been there days and much swearing and bloodletting would have ensued. Not worth it for me. I just went out for a very nice 30 mile bike ride whilst the job was done.
I'm a bit paranoid about getting tradesmen in to do jobs as I end up with so many wildy different quotes and often end up doing it myself, but the DIY option is losing it's attraction these days. I'd rather be out on my bike or down the gym. Tradesmen round here are about £200 a day and I suspect most of them don't have any qualifications.
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