Slightly incorrect, Virgin Mobile give unlimited
free internet as well as unlimited texts for £20. As with 3, the unlimited is limited to a fair usage policy of 3000 texts per month (if your thumbs can stand it) and internet usage is limited to a whopping 25MB per day.
Or alternatively go for the Liberty SIM for £18 per month, which includes 300 minutes unlimited (subject to fair usage) texts, and unlimited (subject to fair usage) internet access.