If Im reading this right, you have a 30 quid amp, 2k phono front end and a reasonable pair of stand mounts.
I'd keep the dino, and by your reckoning you'd then have 700?
I would definately try to keep the dino and spend it on the amp. If you're a real bargain hunter you can get a fantastic amp for the money. Valve kits are good sure, but theres loads of solid state and valve stuff in the second hand shops and classified sections that would really sound great.
Im convinced that the amp is holding back the quality of your tt and phono stage.
B&W speakers (like a lot of others IMO) wake up when they receive some quality power.
Id be looking for something powerful and clean to suit the B&Ws sound.
Here's a few potentials at a couple of shops.
AVI 2000 preamp & 2 monoblocks 800 (a lot of amp, but no longer around if you fry it)
PATHOS CLASSIC ONE integrated amp, few months old as new 825 (like a unico, except it looks good)
http://www.tnt-audio.com/ampli/pathos-classic1_e.html
NAIM NAC 72/ NAP 140 late pair, boxed 700 (second hand Naim holds its value very well. pokey sound - love it or hate it)
LUMLEY ST70 power amp, nice and valvey 700 (I believe Leonard is selling his Lumley passive pre for just a couple of hundred)
I just pulled those up because it shows that you dont have to sell your phono stage to get great amps for your budget.
Those are all from a shop (the emporium which I always do haha) but you'd get a lot more for your money from e-bay or the private classifieds. You'd have no come-back thats the only thing.
Chris