What year is your blade? A 08-11 unit will only fit the 08-11 wheras the 16-034 will fit 08-16. The earlier unit comes up quite a it cheaper though.
Why? eBay is probably the safest place to buy second hand items. If you pay by PayPal you have more protection than you would get buying in a shop. Sellers have to offer a 14 day return and if an item breaks within 6 months you can raise a dispute. Even without Paypal you have some protection in so much as you can leave negative feedback. Buying off a forum you have a big fat ZERO protection.
I would rather get something cheaper, what are the fees to you if your pc sells for £150? time paypal and ebay have taken their fees, £130? i buy all the time from ebay, but if i can save the fees and avoid lining their pockets i will do it every time, i have yet to get burned (famous last words) and that includes buying £1500 plus parts from Canada and Aus.
See my problem with that is a lot of people want me to save them the 10% ebay fees(I pay business seller fee which are a little less) but expect me to sell a £150 item for £120. My combined fees are under 12% + £4 roughly as I offer free post. They dont say sure do it for £140 and I will save a bit and you will save a bit. And that unit will sell for a lot more than £150. I know the market and generally I estimate within 10% of what an item will sell for. Occasionally I am miles out but rarely.