Coolant temp. sender flange leaking, why?

[2.0 8v]

On route to a show today, gave the car a good hard motorway run (120 miles approx). checked all levels prior to departure. Replaced the temp sender and the thermostat housing about 8k ago (stat o ring leaking, replaced unit as a precaution, no issue since). Car has always been a bit smokey(blue) when driving off from idle, nothing major, oil top up every 3-4k. 148k on the clock. Slowed for a toll, one of the lads was parked just after, so pulled in and had a bit of a chat, 10 mins later pulled away. LOADS of white smoke when pulling away, not the usual puff and clear. About a mile later, coolant warning light on, temp gauge at 90. Pulled in straight away. Loads of steam from under the bonnet. Took a while to find but eventually traced the leak to the coolant temp. flange. Dripping like a badly leaking tap from underneath.

Has anyone come across this before? I did drive the wheels off it on the motorway, running late, as usual. Flange is not a major contract to replace, just worried that it might be the result of a bigger problem. Oil is clean, cap is clean, when engine was running (after top up) the coolant did not come out at high pressure. Also no smoke from exhaust when car was running at idle. Got car recovered by the AA and sent back to my garage at home.

Any words of wisdom/advice would be greatly appreciated.