You'll need to check percentages of impurities to find what will work.

Wrought iron would have up to 0.3% impurities, although very little of that is carbon. Let's consider that the standard we need to achieve, because otherwise your plot can't go forwards.

Steel is not necessarily out. High-carbon steel at up to 2% is probably no good, but mild steel will only have up to 0.25% carbon, and (with modern control over manufacturing) probably little or no other elements. That means you're probably good with cheaper nails, rebar, and various other sources.

By contrast, cast iron with around 5% impurities (including carbon) is a complete non-starter, in spite of calling it "iron". So don't bother breaking into kitchens in search of Le Creuset pots, or using a poker from the fireplace.

The problem then is where to get this stuff. As Martin Bonner points out, most exterior metalwork is steel, and has been since mid/late Victorian times. It certainly isn't safe to assume that old metalwork will be wrought iron unless you know for sure. I think the best bet has to be mild steel, all the way. Which basically means a trip down to a builder's merchant to buy some lengths of rebar.

You may also want to try galvanised nails. For sure they've got a zinc coating, but underneath they're mild steel. So the plot would need to know whether the coating is significant when the bulk of the thing is iron. If you're in doubt, buy galvanised mild steel and a linisher, and sand the zinc coating off.

Literally, NAIL your monsters!

How picky are your monsters about the purity of the iron?
Cast iron and wrought iron contain more carbon than mild (soft) steels. Nails are cheap, widely available and a nice, mild steel. Convenient shape, if you can get up close/personal and/or shoot them. The concrete nails typically used in nailguns/ramsets are hardened steel, so higher carbon content than mild steel, but less than in wrought or cast iron (few percent.)

If you need fairly chemically pure iron, grade R https://en.wikipedia.org/wiki/Carbonyl_iron should do the trick!

Average english village? My first thought was to locate a house with a chimney and look for a good old poker. And by good old, I mostly mean old, as it's more than often made of iron and would make for a good bashing weapon.

Of course, that includes to break into a house and steal something, but if iron is the only way to go, I'd feel a lot safer.

It's my first thought without reading other answers. After reading them, it offers a few plus: it's available, you don't have to pry it from something existing like a fenced gate (unless you're the Hulk and can rip apart iron). It's shaped like a stick and make for a ready-to-go weapon. No prep time. You can reuse it: you won't be out of ammo.

On the plus side, in a story, it would be extremely cinematic.

I would run to the hardware store or a construction site for rebar. There should be handy lengths of it lying about.

Another good option (and I'm ripping off Terry Pratchett here) is a machinist shop. Hoover up any and all chaff you can find as well as larger chunks. The chaff could get into their eyes or clothing.

Railroad Rails and Fasteners

Just like an iron gate, fasteners are actually made of steel, but are around 99% iron. In the USA, railroad spikes are common, and can be pried out. In many other countries, screws are used, and may be easier to remove than a spike if you have a long wrench.

Rails themselves are also made out of steel, with more carbon and manganese, but they are both still less than 1% content each, and low impurity requirements, meaning 98% or more iron. Most rail is welded now, so you cant just unbolt some and be on your way, but if you happen to be by a switching station or rail yard, you can dismantle sections that are light and short enough (1 meter) enough to be dragged away by a healthy fit individual, between 40 and 60kg/m for most rail in Europe. If you carry plasma torches or thermite weapons, you can just cut the rail.

Neither the rails nor the fasteners are coated.

The freight rail system itself does transport iron products in the cars themselves, including construction material, iron ore, and metal destined for scrapyards. Britain has a large number of rail lines, and over 20000 miles of track, about 10000 miles in current use.

If I had 15 minutes prep time, I'd head to an engineering workshop. With the grinding, cutting and welding done, there is literally a coating of iron dust on everything.

For a fae to follow you, it would be like you following someone into Fukushima. The very air would be lethal to them from the dust

Normal mild steel has arouna 0.25% carbon as where cast iron is 2.5% to 4% carbon (hence it's brittleness). Ultra high carbon steel is 2.5% carbon

Mild steel is easily found and a purer form of iron than old horseshoes and forged nails.

Hematite

Hematite, also spelled as haematite, is the mineral form of iron(III) oxide (Fe2O3), one of several iron oxides. It is the oldest known iron oxide mineral that has ever formed on earth, and is widespread in rocks and soils.

Huge deposits of hematite are found in banded iron formations. Gray hematite is typically found in places that can have still standing water or mineral hot springs, such as those in Yellowstone National Park in North America. The mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water.