That's the crown/neck

Looks like a healthy dormant bulb, as well as being healthy when it was growing. I think there is enough space in the pot, since some people don't like too big of a pot for amaryllis. However, I've also grown a single bulb in a bigger pot without any adverse effects. If you do choose to repot, now is a good time.

I think your bio feed is what helped it along, though, since your growing medium sounds like it didn't provide that much nutrient. I'd consider a growing medium that also gives nutrient, though based on how some of these bulbs are marketed, you can just grow it in a vase with water.

If you think you want to do that, then have additional soil type to your growing medium.

Personally, I don't like the looks of the soil...but if it grows well for you and you like it, it probably doesn't matter much.

Well. Thank you. I did change the soil - miracle grow with perlite and sharp sand(small amounts) and put it into a square pot.
It's now got a new leaf growing, it's about an inch tall but it's green.

When I repotted it I cleaned up roots removing old and damaged. In the process I weighed the bulb, 382grams and it's huge bulb.

I'll be buying more should I find any from same seller. I bought loads of good stuff from them! Namely pink daffodils!!
Thank you both

One thing I found is that with the amaryllis bulbs being sold in the winter, usually for an indoor bloom, they would go on sale/clearance at the end of winter. At that time, buying them and planting them up outside for the spring, they would still bloom and grow just fine.

So be sure to look out for amaryllis bulbs on sale during and after winter, also.

gardenper - I've never come across anyone managing to grow Hippeastrum outdoors in the UK. Even if they grew, which I doubt, the wet and windy spring weather and the slugs would finish them off. I know about the slugs from bitter experience. I put mine outside after they've flowered indoors and they invariably get chewed to stubs.

However, I have bought them after Christmas and had them flowering indoors in Spring.

agree with Floral_uk the weather is just terrible at that time of year. And thw slugs are a menace!
So it doesn't matter when I buy it? Weather it be now or February! Nice. Tesco has just started to sell the preforced bulbs! I just bought the paperwhites as was cheaper than the iron mongers (only other place selling bulbs)

Okay. I thought thw bloom comes first? Mine as a single leaf, I know that some bulb won't flower for a few season after being forced. Shall I just let it grow bigger and bigger?
Slightly odd question, (more why would you do that statement)
If I wanted to grow a huge bulbs, can I just cut t the flower stalks off before they fully grow to. Height?
Can I do the above with all bulbs?

you'd be better asking your questions in amaryllis forum.
your bulb went dormant in early sep; it needs 2-3 months of dormancy (dry/dark/cool place) before restarting again. why are you encouraging it to grow now?
there are some unorthodox methods of pulling the whole plant (green leaves and all, leaving soil intact) out of the pot and drying it for a week and then potting up...that some people experiment with. but that is usually in warm zones with good sun in winter (like in australia many hippies are evergreen).
but there is also the danger that the plant will spend it's energy growing leaves now instead of blooming. there is a light 'problem' in winter too: unless you give it extra artificial light , the leaves will be very weak and lanky. even southern window won't do it. and it does need direct sun, not just bright light to grow properly.
you need to stall regrowth by keeping it very cool and with minimal moisture (at 55F min).
it'll need 4 weeks to reestablish roots, even if you had some left (i hope you did not cut off healthy white roots!). but if you put it in the warmth now it'll start growing leaves without adequate root support.
it'll be good to confirm with specialists, of course. as i just rebloom common minervas and this is 'a tricky situation' you created, for sure