They are unlikely to grow much bigger now but the only thing you should be concerned about is leaving them so long that they start to rot if the ground is still very wet. I would tend to lift them now and get them dried somewhere for storage.
Don't just pull them up, but raise them with a fork or hand fork to break the roots and leave them for a day or three to dry before harvesting. Easy to say if it's raining continuously I know.
Must admit I've left some of my onions in previous years right until the end of October before finally harvesting them and that caused no real problems.

Most of my onions are exactly the same. Mine are still growing. You can tell by looking at the tips of the newest leaves. If they are growing upright, even though the others are flattened, then they are still growing.
Your onions are ready when you want them to be. If they are a good size then either get them up and dry them off in a warm airy room for a few weeks, or lift them in the garden to disturb the roots and let the sun.....that is a yellow object that is found in the sky..... ripen them naturally.

I've never had the tops of my onions be so bad so I can only assume it's weather related. Quite a lot of splitting this year as well, so i'm getting mine up as and when to prevent anymore damage.

Thanks again, guys, I asked the question, went into the garden for a short while and on my return my problem was solved.
As it's the best day for ages I'll have them up ( with fork of course) after I've finished my morning coffee and biscuits.

Ive pull all mine up today. Some were rotting on the top so they are up and luckily its sunny so they can cure for the day in the sun.

I suppose really it depends on which area of the country you live in. The soil type also affects them. Sandy soil out on the East Coast would be drier. One year our allotment Steward came round telling everyone to get their maincrop onions up, as they were all getting Grey Mould, and would not keep. Seems this virus stayed on that field, as my Grape Vine crop was ruined by it. (I later moved.)
About the Onions, I dug all mine up in a panic, cut the mouldy tops off, dried them off in the greenhouse, cut up and cooked in the Microwave and froze. They lasted most of the winter. I use one organic Onion a day for health reasons.