Hello, I'm TV Tech1 and I'll be working with you to identify and help you resolve your problem.
It sounds like your TV set is good since it gives a great picture of the photograph...but it sounds like the SKY+ box may be sending a low definition picture to your TV set since it's blurry and the text is too.
Tweaking the lens is ok, but it's unlikely the issue. The SD card's results seem to prove that.
So...how do we set your Sky box's video output from 480/
540 low def signal to 1080i high def signal? It would have to be in the Sky box's menu, and it's important to know if you are watching a LOW DEF TV SHOW on a HIGH DEF TV CHANNEL or if you're watching a LOW DEF TV STATION.
Look at the Sky box's TV Guide. It should show HD on the TV channel and HD on the TV show. Then you know it's all HD.
And if it's blurry, then you know the Sky box is sending a Low def signal to the TV set, and it needs changed in the menu. The resolution setting is usually found in the video submenu under Video output or resolution setting.
I don't know the Sky box's model number so I can't give you specifics...just generics found on all boxes.