Looking at the Sony catalogue, the two models look remarkably similar in design. Looking at the spec sheet, they have the exact same dimensions too. I suspect they are the same TV cabinet, but for some reason they supply a different cabinet with each. I agree, the glass fronted cabinet looks more like it should be in the kitchen than the lounge!
I guess you might be able to get the cabinet as an extra purchase. I personally would go to an independant Sony dealer, and try and do a deal , maybe say you're prepared to pay a bit more if they swapped the cabinets over. If they're the same, the shop may not mind too much selling one TV on the wrong cabinet. After all it's only a cosmetic thing, not structural.
I'd hazzard a guestimate price of £150 - £200 for a new cabinet. YES they are VERY expensive to purchase seperately.