First person narrator

Struggle with finding the right tone for first person narrative but keep trying to get it right. This is the beginning of a short story I've just finished. I'd be interested to hear any comments re whether it sounds convincing or not. Open to all suggestions for improvement!

                     Ladies Who Lunch      
                    © Christine Findlay


It’s the middle of the night, - well, maybe not quite but it feels like it.  Cold, dark and raining - that fine Scots drizzle that manages to penetrate even the most ample flesh and seep into the bones.
    So, what in God’s name am I doing here? Okay I know I was invited, if you can call Grace’s late night summons an ‘invitation’.
    “Olivia’s called off, I’m afraid. Nigel’s made her a better offer. Need you to make up the numbers, Jane. Megabus leaves Broxden at 8. See you then.” And she hung up.
    Verity and Grace (anyone less gracious I’ve yet to meet) are huddled in the cramped bus shelter when I arrive, damp and breathless.
    Grace, not a hair out of place, greets me with a royal hand movement - not quite a wave, more a wavelet.
    “Sorry, no room,” she mouths with relish, indicating the crush.
    I smile forgivingly and curse myself for having left my umbrella sheltering the kitchen table.
    Five minutes later, the Edinburgh Megabus emerges from the gloom, her sunshine yellow logo lighting up the grey November morning.
    I dive into my handbag, searching for that passport to exotic travel - the bus pass. Oh, joy of joys - don’t say I’ve managed to forget that as well. I look up ready to signal the ‘bad’ news to my two companions, only to discover they’ve sailed past me and into the warmth. Verity beckons me to hurry. I mime frantic searching, then overwhelmed by guilt pangs, pull my hand out brandishing the card. Grace winces at this public display. She regards advertising our age as a mortal sin.
    “Morning, Jane. Organisational problems?” she quips.
    “Er . . . sorry about that,” I stammer, collapsing into an aisle seat whose leg room seems designed to accommodate the vertically challenged.
    “Very comfortable,” enthuses Verity, patting her chair. “Roomy too.”
    I make a mental note of the position of their seats for the return journey.
    Verity’s looking particularly prim this morning. Her face is thin at the best of times but today it seems pincered as if she’s been sooking extra strong peppermints. The hairstyle doesn’t help, of course - short, sharp and steely grey
    The bus pulls out and we’re off. Three ‘mature’  - connotations of ripening Brie - Perth ladies hitting the capital for a spot of retail therapy and a bijou dining experience. I let out an audible sigh and draw looks from ‘Powerful’ and ‘Prim’. How am I going to get through the day?