activeuk
Better to purchase a single piece cable HDMI2DVI now and if required you can add in a converter at a later date - you can convert DVI to HDMI just as easily as HDMI to DVI.
See
http://www.hdmiplanet.com/adapters.html
Ensure any long HDMI to DVI cable you purchase is on sale or return - especially so when its DVI at the receive end; not all cables are created equal and depending on what signal your trying to send over 10m you can get varied results.
If I understand your figures your saying you can get a 10m HDMI cable + an adapter for a total figure of £60.00 - that's a mighty cheap cable.
Best regards
Joe