[AlaninCarlisle]

I have half a dozen apple trees that are about 30 years old. They crop quite prolifically but the apples are quite small. The trees are about 10 ft tall and have never been pruned. I'd like to get them to a more manageable size and hope at the same time to increase the size of the apples.
They are Egremont Russet, Golden Delicious and Cox's Orange Pippin plus a couple where the varieties are unknown other than that they are eaters.
Any tips on when and how to prune them would be much appreciated please

[Lardman]

Probably the easiest way to follow and understand the techniques is to spend a while watching some of these https://www.youtube.com/user/stephenhayesuk  Taking a few big cuts in winter rather than lots of little snips in summer is probably your best bet. If you want to drop some pictures up after leaf fall I'm sure we'll all give you lots of differing suggestion on how to prune them 

If you don't already do it get a good mulching of poo around the base of the area at least 1ft in diameter, get some life back in the trees. ER and COP are smaller apples though you'll have to thin hard to get shop size.

[Yorkie]

You might also want to consider phasing any major rejuvenative pruning across a couple of winters; that's what I did with my very old apple trees in my garden

[AlaninCarlisle]

Thanks to you both. I've bookmarked that Youtube video and will follow its advice as soon as winter takes a hold.
As far as putting muck around the base of the trees is concerned, I've been doing this for years as it seems to prevent those horrible black spots (bitter pit?) that the Golden Delicious in particular seemed prone to. However this flew against the advice of old neighbours who claimed that it created leaf growth at the expense of fruit.

[AnneB]

I haven't watched the video so this might duplicate.  A fellow plotholder on our site has done a proper fruit course.  He has dealt with our similarly overgrown cooking apple on our plot over the last 4 years.  As Yorkie suggests he has phased it in over a few years.  First year he pruned back some of the cross cutting overlapping branches with the aim of working towards a tulip shape and a little of the height.  Then he did more thinning out crossing branches and more off the height.  It now looks more like it should. Last two years the crop has been great and we no longer have fruit going brown on the tree.

[solway cropper]

At 10 foot high and 30 years old they must be on a dwarfing rootstock which means they are getting close to the end of their productive life. You can prune them as suggested but I'd be inclined to grub out and replace a couple every few years. I have a similar size James Grieve which produces huge crops of golf ball apples so it's coming out this winter. I replaced an old Egremont Russet a few years ago with an Elstar which this year is absolutely laden with gorgeous fruit. Fruit trees (and bushes) have a limited lifespan and sometimes it's just best to let them go. As a bonus apple wood is great on an open fire !