Feral cat behavior

Hi I'm new here, iv joined to hopefully get help in figuring my unpredictable cat out!!
First off a quick backstory.... I lived in an area that was overrun with feral cats (I know the difference now between feral an stray) I had a car sat in my garden while trying to sell it but had attracted a feral cat which was using it to store her kittens in the engine, I'm not sure why but she would leave 1 at a time for a few days then swap the kitten with a different one. one day wen I had someone viewing the car I found a kitten covered in oil so I managed to capture it and bring it inside, sadly after this the mum never came back. the kitten hid under my bed an slowly over few days came out but would hiss an run back under if I went towards it. eventually after a month I'd gained enough trust for it to come to me but only wen I sat on the bed (I think maybe being sat lower to her level) the kitten was barely 6 weeks old an fit in the palm of my hand. over the next few months the bond grew to the point where she would follow me from room to room like a dog, she's now 3 years old and is like my sidekick, she comes to bed with me and even gets under the quilt to squash up to me, However on the flip side she won't allow me to pick her up, will sit on my lap for no more than 5 minutes and if I stroke anywhere other than her head she growls an swipes (she growls quite a lot). can anyone explain why she's so so loving yet so so mean at the same time?!

It sounds more like a personality quirk than the result of her being feral.  She may just not appreciate being held (lots of cats don't like it).

Also, many cats don't like being stroked anywhere but their heads.  Their nerve endings are very sensitive and it can actually be painful to be touched in certain area.

I would just allow her to be herself and enjoy whatever limited touching/petting she allows.

I have a cat - eight years old - who I have never given more than a ten second head scratch.  He's a sweetheart but just doesn't like touched.  He lets my husband pick him up for about 15 seconds, then he wants down!

Ritz was part feral/stray when first trapped (dumped when she was around four to five months old with her litter mates, no significant contact with humans before then, except the (in)humane person who dumped her).
Ritz still hates being picked up (and Ritz is my first cat so I didn't really know how to pick up a cat). But she will sleep with me and has grown to love belly rubs. At first I would just pet her tummy a short second or two and see how she reacted. Then a little longer until now she deliberatly turns onto her back for a belly rub. Still, I watch her body language and try to stop before she gets even a little bit 'petted out'. Too much of a good thing can turn bad.
On the other hand I fostered a formerly owned, dumped cat for a few months. Super friendly, very low key. He never wanted to sit on my lap, but would spend minutes/hours by my feet (like a dog).
It sounds like a personality quirk.

Welcome to TCS! 

I have had my 2 since they were about 11 weeks old. They were picked up with their mother and 2 litter mates in a nearby town.  Mooch would glue herself to me if she could.  I used to walk around with her on my shoulders; wrapped around my neck like a scarf.  Noodles; well 9 years later we still have to let her smell our hands before we can pet her.  Sometimes she swats at us just for walking by her cat tree.   She will sit in my lap; but it's got to be on her terms.  She goes through cuddly phases and ones where she prefers to be left alone.  I don't bother with trying to pick her up much because I don't think it helps her moods.    She will tolerate it for a short time; but I really don't think she likes it.  I just accept it as who she is.  She is my alpha when it comes to food time; but Mooch is when it comes to lap time.  So you can see; even litter mates can be very different.  I think their mother may have been dumped or less likely, in the semi-feral category.  She was also up for adoption when we adopted our girls; so she was at least adoptable herself.  I remember a cat who looked a lot like Mooch does now that I saw sitting there just calmly watching people.  

I agree on it being most likely a personality quirk.  It may change over time still.