I am also delighted to find people who love Rubbra. After Vaughan Williams, I would put him at the very pinnacle of English composers. I actually bought my Chandos set of symphonies blindly after a recommendation that suggested he was another VW. I have never been sorry, and particularly favour symphonies 3 & 4. Big thumbs up for Rubbra.
I am also fascinated to see so many others of my favourite composers listed in this quoted post! VW, Tubin, Holmboe, Bruckner, Shostakovich.... I am poking around in Miaskovsky atm, to my great delight
Coincidentally I'm listening to Rubbra's 10th Symphony at the moment and had forgotten how good it is. It features on a fine old Chandos CD with the charming Farnby Improvisations an 'A Tribute' (to Vaughan Williams) - a lovely CD.
I'll be very interested to hear what you make of Miaskovsky - we have similar tastes. I'd recommend the Cello Concerto + symphonies 3,5,6, 11,15, 16 (great funereal slow movement), 17,21,24 and the valedictory no 27.