Hi , i'm looking to buy a 1907 pattern wilkinson bayonet and was wondering how much i could expect to pay . Also any suggestions as to where to look and and what to look for and what to walk away from would be a great help , thanks . Steve .

There are plenty of 1907 bayonets getting around on eBay for around the 20 pound mark, but, while they are generally fine examples, what you get is a bit of a lucky dip.
If you're after "just" a 1907 bayonet, that's fine, but if you are a Great War collector, it will be a bit of a quest.
Like rifles, bayonets were serviced ... there are plenty of 1913-1918 .303 rifles getting about that were re-built as much as three time after the war - sometimes as late as the 1950s.
So it is bayonets - you'll find plenty dated 1908-1918
manufactures, but most you'll encounter will have post war inspection dates and various obscure "chicken scratch" ownership markings.
Only in very rare cases will you encounter a 1908-1913 British bayonet with an intact hooked quillon, but what many collectors don't realise is that from 1913 to sometime in 1916, Pattern 07 bayonets with the straight hilt did not have a clearance hole, which was often drilled during refurb.
The only intact "Great War" bayonet in my collection is a March 1914 Enfield which has never been refurbished. I have also been lucky enough to land a 1913 Enfield which had the quillon lopped in 1915 but no clearance hole drilled, and a 1911 Enfield which has no inspection marks and has had the quillon roughly removed, perhaps at unit level.
None of these bayonets cost me a premium, but it did take a bit of sorting through literally piles of bayonets to track them down.
So to answer your question "garden variety" Pattern 1907 bayonets are plentiful and cheap, but intact Great War examples are harder to find, and will not necessarily attract a premium price.
This very nice JAC (Chapman) December 1915 Pattern 1907 in original condition without a clearance hole and minus a scabbard recently went for a "buy it now" price on eBay of 85 pounds:
http://cgi.ebay.com.au/ws/eBayISAPI.dll?Vi...p;rd=1&rd=1Sure, it was a bit more than you'd pay for a bayonet with scabbard, but I don't think it was outrageous.
Here's a few of the bayos from my collection (Enfield 1913, quillon removed in 1915 but no clearance hole drilled in the pommel. There is a 1915 inspection stamp on the other side of the blade - which is where you find them - but the bayonet is in the conifguration it would have served throughout the Great War):