Hey all, thank you for thinking of me.
To update the thread, towards the end of this last week I became increasingly hysterical and decided to take myself down to the Fetal Medicine Centre in Harley Street for an appointment with Professor Nicolaides. I think it was out of sheer desperation really, I just wanted an answer...any answer, rather than nagging and annoying my consultant when I knew he couldn't tell me anything more without the MRI results.
My appointment was about 2 1/2 hours behind schedule (a note if you ever need to go), but they do tell you to phone beforehand to check delays and with rush hour traffic I waited just over an hour.
The sonographer I saw was nice, checked the baby all over very thoroughly, but once again she told me she'd never seen anything like it before and couldn't guess what it was. BUT she said, if anyone would know Nicolaides would. After about 30 mins of scanning Nicolaides walked in and in the space of 5 mins - took a peek, determined that it was probably a teratoma, that the baby could possibly be saved 'if' I choose to continue the pregnancy, that I should go back to my consultant insist on an urgent referral to GOSH, and that btw teratoma's can grow to be 'massive'. He then left the room 
So if anyone saw me leaving the waiting room that day, I was the one with bright red eyes - eek! Needless to say I felt worse than ever following that app, so the following day I rang the hospital in tears asking to speak to someone and to their great credit the lovely receptionist/midwives listened to me and slotted me in for a quick chat with my consultant on Friday between appointments.
Luckily enough my MRI results were in and the diagnosis is now most likely a Lymphatic cyst, also known as a Lymphangioma. The location at the base of the tongue is unusual and according to the results it is taking up most of her oropharynx at present so complications to some degree are almost inevitable. I was told off for Googling myself into a frenzy and my consultant seemed mildly optimistic, but to be honest he is sooo laid back I can't tell what he might actually be thinking. I think the main issue with lymphangioma's in this location is they cannot simply be cut out completely, and he mentioned the possibility of future issues with eating and speech.
He said the next step is an appointment with a pediatric surgeon at Great Ormand Street Hospital in the next couple of weeks, and further monitoring of the growth. I didn't ask about the prognosis, but termination was sort of mentioned in a roundabout way...I'm guessing if in the near future they feel that operating is futile the choice is there. It's not something I'm entertaining at present.
So...that's it so far. My next appointment is on Wednesday, and from there I should hear more about meeting with the pediatric surgeon and an update on the cyst's growth (not sure I want to know this though).
I have to admit I am feeling a little bit better now I know more, but I'm still aware that there is a long road ahead and many risks involved.