In CQ-TV 242 John, G4BAO, published a design for a 2.5 watt LDMOS driver amplifier. This is a very useful driver circuit which John sells in kit form on his website which when driven by a Portsdown / DATVexpress transmitter will deliver around .5 watts (to be confirmed.) of clean DATV signals.
In CQ-TV 249, Clive G3GJA published a review / designs notes on 2 watt amplifiers available from ebay. (The full article is available in high resolution in the magazine)