Left employer, L1 not cancelled. VWP?

[orchover]

I am a UK resident and I have an L1 visa with an expiry date of Dec 2011. However, I no longer work for the employer who sponsored me. My former boss has tried repeatedly to cancel my L1 visa over the phone without success. The US embassy keeps you on hold on the phone at £1.20 a minute for 5 minutes, then cuts you off and says no operators available- try later, so my boss says he isn't prepared to waste any more money trying to cancel it.

I am hoping to visit the USA for 4 days holiday in August. I won't be working. How should I enter the USA? Should I just use the L1 visa? Or should I enter under the VWP with an Esta?

[immihelp]

VWP and ESTA.