Neolithics made it to the Addaman and Nicobar Islands. Any trip by Neolithics to Iceland could use the arctic ice sheet for shelter and make a series of staged trips.
http://www.daftlogic.com/projects-google-maps-distance-calculator.htm
Well, using this to do some ballparking, we find that the nearest shores of Iceland are approximately 270 to 300 miles away from the Faroe Islands, going due northwest.
From the Faroes, its a 200 mile jump to either mainland Scotland or its northern or western Islands. It's almost 400 miles from the Faroes to the closest point of Norway.
Direct route, as the crow flies, its 600 miles from the closest point of Iceland to the closest point of Norway.
Now, let's take a look at what that means to Neolithic cultures.
Assuming that they're crossing over ice floes, gee whiz, how fast are they moving. Let's assume a steady march of 10 to 15 miles a day, average out to 12. That's pretty good time actually. These are people on the move - literally - say 8 hours to sleep, a 4 hours to stop and eat, go to the bathroom, look after stuff, mend your tack and harnesses, take care of the children, rest, prepare.
Assume 12 hours of marching a day, 12 miles a day, works out to 1 mile an hour, which when you're considering that they are fully loaded and have to be carrying a lot of stuff with them... that's pretty good. But suppose we doubled that up to 2 miles an hour, 24 miles a day.
From the Faroes to Iceland, assuming a direct route as the crow flies, minimum of 11 to 12 days.
From Norway to Iceland, well that's 25 days.
Of course, in winter you don't get a 12 hour day. Up around those latitudes, your winter day might be as short as 8 hours. Considering that a lot of what they're going to have to do - including food prep, takes place mostly in daylight, they've really got only 6 hours. Assuming that they keep to 12 miles a day, that's 2 miles an hour, a walking speed for unladen people, that's damned crazy good.
In which case the trip from the Faroes to Iceland is 22 to 24 days. From Norway to Iceland, that's 50 days.
This is the best case scenario.
Now, that assumes near glacial conditions, of sea ice encapsulating Iceland and extending continuously all the way down to the Faroes.
And it assumes unbroken sea ice, no open water spaces, no giant temporary mountains of piled up sea ice. No treacherous thin areas. That's not likely. Ocean currents move sea ice around, they move it back and forth. Wind piles up. It's always in motion, creaking, cracking, piling up. The further and longer you are out on sea ice, the more dangerous it is. Most likely, you're going to be taking lots and lots of detours, switchbacks and wrong turns.
That's not even considering that the winds and the currents are going in the wrong directions, all of them.
It assumes that they miraculously are carrying a couple of weeks or a couple of months worth of food, water and fuel that are going to keep them alive on the trip, because lets face it - there's not going to be any fish, game or vegetation along the trip, and you don't want to try and drink melted sea ice. It's likely that any animals brought along will die and be eaten or abandoned. That any plants or seeds will be consumed.
Most likely, they die on the ice. Maybe one chance in a million, someone makes it to Iceland, where they die. Maybe one chance in a hundred million, a few people of mixed genders make it to Iceland, in good enough condition to survive and keep reproducing - but in that case, most of their inherited culture is going to be lost or abandoned to survival - they have no domesticated animals and there are none here to domesticate, they have no domesticated plants and the wild plants aren't suited to taming.
Sea travel during the summer is a better bet. But there you'd have to pay close attention to the currents and the winds. You're still looking at a passage of several hundred miles.
And there isn't anyone in the area with all that much of a sea tradition.