Don't know much about these tipi tents but I bought a 5m bell tent from these guys and at £180 incl post it was at least half the price of all the other suppliers - and my tent is excellent, well constructed, no complaints at all.
http://www.cybercheckout.co.uk/p-58-tipi-12-person-family-tent-teepee-sale-price-free-pp-.aspx
http://www.cybercheckout.co.uk/p-58-tipi-12-person-family-tent-teepee-sale-price-free-pp-.aspx