have there been speed restrictions imposed recently for the tt 2 weeks for visitors

Don't know about TT Festival specifically, however the DOT post new speed restriction notices regularly on their web site, for instance:-

The Department gives notice that it proposes to make an Order the effect of which will be to impose a 20mph speed limit on the following roads in Laxey:

The B58 Church Hill and Glen Road
The C551 Captains Hill Road.

A draft copy of the Order with plan is available for inspection at the Department's main reception desk on the ground floor at the Sea Terminal, Douglas or the office of Laxey Commissioners by any person, free of charge during normal office hours on or before Tuesday 6 May 2003.

Any person, wishing to make representations on or object to these proposals should do so by notice in writing to the Director of Highways, Department of Transport, Sea Terminal, Douglas, IM1 2RF on or before Tuesday 6 May 2003.

or

The Department gives notice that it proposes to make an Order the effect of which will be to reduce the speed limit from 40 mph to 30 mph on the A23 Braddan Bridge/Mount Rule Road and the B22 Mount Rule/West Baldwin Road in the Parish of Braddan.

I suppose really that common sense should prevail and that whenever you appear to be entering a built up area, you should automatically look for the posted speed restriction and comply with it. Outside of those areas, then it's business as usual I would presume. However, as we all know, there will always be those who disregard the posted speed restriction notices and get caught.

Break the law, you pay for it. It's as simple as that.