Growing and Seed saving with my 'Neeps' (rutabaga)

I've been growing Swedish turnip (Neeps in Scotland, Swede in the rest of the UK and Rutabaga in US) for the first time this year. They have done really well, I have lots of a good size. The only problem I had over the summer was that they did rather too well and have shaded out most of my carrots and parsnips which were in the same bed.
I have harvested a couple in the last month or so and I was imagining leaving them over winter since we have a pretty mild winter most years and I think they should be frost hardy here. I want to let some of them to go to seed next spring to cross in a landrace project. It looks to me like some of them are already starting to think about going to seed - the stems are thickening and lengthening. I'm assuming these won't  be the best to eat now as they will getting tough.

first year neeps

So my question in this: How do I select the ones to grow on for seed, and which to eat? I sowed at least 4 different varieties, some of which look as if they have similar colouring, but made the mistake of mixing up the seed in the bed. Next time I will know to sow the seed separately so as to tell the difference between the different sorts.
The other question is - In the future when I am developing my landrace, how do I chose which roots to breed from - particularly how to select for flavour when you can't tell until you've cooked them?

Nancy said, "So my question in this: How do I select the ones to grow on for seed, and which to eat?

That is a hard question to answer.

To me, the easy answer would be first select the best plants for seeds and eat the others.

Though there maybe other traits a person might want to save seeds for.

Here are some threads that might be of interest:

https://permies.com/t/119976/Saving-seeds-Basic-information

https://permies.com/t/162810/start-seed-saving

https://permies.com/t/177487/Seeds

https://permies.com/t/46886/Saving-Seeds-Breeding-Plants-Landrace

Well I've come up with a plan for selection this year.
I actually harvested and ate one of the roots with larger stems yesterday; the stem was about 6 inches long and about an inch in diameter so I thought if any were going to be woody that one would. To my surprise it cut like butter and cooked up beautifully, so either it was a variety that doesn't go woody quickly, my climate grows particularly tender swedes, or they don't go woody till the spring. I think I need a turnip knife to trim the leaves and roots off the 'bulb's.
So the plan is to dig all the roots up and sort them by size and degree of shooting, then select about 12 varied ones to grow on for seed. I'll plant 8 and keep 4 in a coolish place safe from mice just in case. The rest of the roots can be stored and eaten or sold.