Hello and welcome, JD ~
I'm sorry to learn that you've been diagnosed with an acoustic neuroma but glad you found the ANA website and decided to post on the forum. We're not doctors but collectively, our membership has a wealth of practical experience in dealing with an AN that they are eager to share with you, as you're quickly learning. Your tumor is very likely too large to be safely irradiated but a physician will make that determination. While brain surgery is not what anyone really wants to go through it isn't the end of the world, either. Many of our members are running marathons (well, half marathons, anyway) within months of their surgery. Others engage in equally strenuous physical activities. Many have young children and/or jobs that they mange to take care of. It isn't all 'gloom and doom' by a long shot.
For what it's worth; I was 63 years old and diagnosed with a 4.5 cm AN in May, 2006. I underwent a partial resection of the tumor - with almost no complications, then, 3 months later, 26 sessions of FSR (Fractionated Stereotactic Radiosurgery). This was a carefully-planned attack on the large AN, intended to spare the facial nerve and, ultimately, destroy the tumor. I can report that it was highly successful. My experience is not necessarily an anomaly, by any means. Granted, AN removal surgery has inherent risks but it is usually successful and very often, even those AN surgical patients that experience problems (facial paralysis and attendant issues) find those deficits to be temporary.
As many will admonish, to secure the best odds of having a good surgical result, do the necessary research and definitely seek out a surgeon with copious AN removal experience. That is critical. I'm sure some of our UK members will offer some suggestions on that. Meanwhile, take a deep breath and remember that the tumor is not malignant and, as Phyl (ppearl214) stated - treatable. I'll add that although acoustic neuromas are relatively rare, you're not alone in this battle. Many are with you and will support you in every way we can. That includes me.
Jim