I wouldn't go with the series connection across 230VAC, that is just asking for something really bad to happen... :o With a possibility of 120VAC potential difference between the chassis, this could be an electrical disaster in waiting... :o There WILL be AC hum problems, galore. :o Light bulbs, maybe, but MK3s, never... Yellow_Light_Colorz_PDT_11
If you are a "purist" and want to preserve the looks and aesthetics, and don't want to mess around with external isolation or step down trannies, Triode Electronics does have a Euro-Voltage version of the P782 power trannie, at around $140 each, plus shipping:
http://store.triodestore.com/p782sexp.html
There is a Hammond "300 series" equivalent, the 378X, but the fit and finish are not identical, as the mounting dimensions are somewhat different. AES has it for around $119. USD
Triode also has an ST-70 "export power" version, as well.
The lower-cost approach is to find a 1KVA step down (and isolation) trannie, rather than one of the single winding "auto-transformer" type step-up / step down types.
SPecially made "universal" power trannies could be fairly costly, but the isolator / conversion trannies are common and relatively inexpensive.
Trafomatic could probably create one (if they don't already have it as a stock item) with 230VAC input, 115VAC output (this would would also translate to 240 in / 120 out).
I've seen various toroidal "isolation" trannies with four windings, basically two 120VAC inputs, which can be wired in series for 240VAC, and also two 120VAC secondaries, which could be connected in parallel for 120VAC, or brought out as two separate 120VAC windings. This type of transformer is fairly common, I'd go for the 1KVA version, (1000 Volt-Ampstotal capability) as it will run cooler and quieter (less vibration and mechanical 50Hz mechanical buzz / hum) . The extra VA capacity allows for running additional pieces of 120VAC equipment if needed, for your audiosystem.
I.ve used smaller, lower VA capacity versions for 120VAC input and 240VAC output, for generating relatively high-current B+ of 250VDC.
/ed B