Export of Placenames?

I'm afraid this probably doesn't readily exist. But for sure it is possible to generate this, although this require the use of more advanced techniques. I could imagine two different approaches:

Filter the data locally from downloaded data

First you have to get the country extract for the UK e.g. from Geofabrik. Also you have to get Osmosis and familiarize yourself with the usage. Osmosis allows you to extract all place nodes, use something like --tag-filter accept-nodes place=*. This gives you an XML file containing the information, you will have to reformat it somehow to get the list you're looking for.

Use Overpass API to get the data

Overpass API allows you to do the filtering directly. Here you'll have to use something like < has-kv k="place" />. But doing so for all places in the UK might be a bit to large of an request. For an easier interface you could have a look at overpass turbo.

As an example, here's what I did when I wanted all the railway stations in mainland GB. You'll need to think about what "place=" items you want to keep and amend accordingly. If you want Northern Ireland as well, then you'll need to include some from an Irish extract too - it might be worth asking another question about that.

1) osmconvert great_britain.osm.pbf -o=great_britain.o5m

2) osmfilter great_britain.o5m --keep="railway=station" > stations.osm

3) osmconvert stations.osm --all-to-nodes --csv="@id @lat @lon railway name" --csv=headline > stations.txt

4) Open stations.txt in your spreadsheet program of choice, and remove lines that don't have "station" in column D

Step (1) is needed because osmfilter doesn't understand pbf (protobuf format) files. You could process as a raw .osm file, but it'd be much bigger.

Step (4) is a sanity check to get rid of a few bits and pieces.