Hi, If you want a bit of height for the crossing you could go via the North Wales coast.. fl.065 and fl.075 at Llandudno. BUT if you need vfr conditions, these are few and far between. I tried a vfr crossing and the ATIS gave Few at 1000ft when I was over Wales, which turned into Broken at 0ft half way across the Irish Sea. (I diverted to Caernafon.)
I have been looking at the IOM Manx Radio Webcams most days and really good vfr only occurs for about 3 days a month.
If you do get there, try out their Manx steam railway for a trip into Douglas, and the Manx Electric Railway for a trip up Snaefell.
Best of luck... Pete