Check the back of a packet of persil. They may still be running that helpline to help you deal with different types of tough stains and you'll get the number there. Obviously most advice is geared towards selling more persil but they were fairly good at other tips too (it's a couple of years ago now, don't know if it's still going.)
As it says on the [broken link removed] site check the care instruction first. Under normal circumstances IMHO your best bet is to bring it to a reputable dry cleaners and ask their opinion.
A polyester/nylon mix might have washed out no problem but silk is a different matter.
P.S. If you do decide to use the baby wipes as recommended below or any other stain remover make sure to test them out first on the back of the tie where any possible fading will not show at a later stage.
Use a baby wipe - they're quite powerful in getting rid of stubborn stains and used with a little care should not cause any damage to the garment. They're also comparitively cheap - 80 for around €2-€3 depending on where you buy them.
I have tried the wipes to which Jem refers (afaik ou can buy them in Clery's or Arnotts as well) but I found them useless.
Stain devils - available in Superquinn (and others I'd guess). It's a packet of foiled-sealed wipes.
They have a range of options depending on the type of stain. They also have a disclaimer warning against use on silk but on the basis that my tie was otherwise ruined I took a chance and it worked fine. It goes on wet but drys quickly.
Baby wipes as suggested by Tommy. Find them fantastic for almost any kind of stain - particularly the Aldi ones. Makes you think about what is in them though!
slightly off-topic but I find the baby wipes are great for giving the interior of the car a quick shine up - as you say, makes you wonder what's in them.
No solution to the tie conundrum though - buy complex patterned ties in the first place perhaps, stains really stand out on single colour jobs?