I have a bird of paradise palm which has grown to double its size since I purchased it last year. Its yet to flower but I have noticed theres extra shoots coming out from different parts of the soil with smaller leaves. Do I have more than one plant and should I separate them out?

Extra pic

Thanks for the advice

White Bird of Paradise (Strelitzia Nicolai) isn't a palm. Its an herbaceous plant that comes from South Africa. Yes, you have more than one plant, because like bananas, these plants sucker and make lots of offsets.
Your plant is extremely juvenile in spite of what you consider being a large plant. These typically reach heights of 18-20+ feet and will not flower until more mature, like these pictures.
You should just leave all the plants alone in the container until its gets crowded and root bound then step it up. Unless you live in USDA climate zone 9B and up (or 9A with an extremely good microclimate) you should not plant this out, a freeze will set if back

Thankyou for the wonderful info and advice. its much appreciated. im in the UK so it will stay in side. I had noticed some of the leaves had some yellow spots on but couldn't work out if it was sun burn or under over watering. Here's a better picture.

For reference I water about a cup once a week. each time checking about an inch down in the soil to see if it's dry.

I think you are running it too dry. If its warm you can put it outside. They grow here outdoors and have survived the low 20's (20F, I'm not sure what that is in C). They grow actively in temps above 50F, 60 is better. I'd saturate the soil completely once a week and let it drain and dry out. You should water it so that water runs out all the drain holes, so that you are certain you are saturating ALL the soil. Underwatering creates dry pockets in soil that become hydrophillic (shed water) and can lead to root loss, just like keeping it soggy all the time can lead to root loss

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Lovely Giant White Bird of Paradise (Strelitzia nicolai). They can probably survive short periods with temps of -3.9ºC (25ºF) but continued cold would likely kill it. Your plant is definitely producing offsets which could be removed and potted up on their own, or left to continue growing with the original plant. If it were mine, I'd leave them to grow with the mother plant, which will eventually need a much larger pot.

The discoloration on some of the leaves is likely moisture related, either too much, or too little water. I always advise watering container plants by thoroughly saturating the entire soil mass until water is freely exiting the drainage holes of the pot and emptying all excess water from the catch tray. Although they are drought tolerant, when grown as a container plant the soil should be consistently damp throughout, never overly wet and not allowed to go completely dry for extended periods.

Here in Florida they are common landscape plants and they grow really, really large! The photo below from our database entry (at the blue link above) is a tree growing in my neighobors yard: