I feel my honour has been slighted and I need to vindicate myself ;-) See variations on a theme
Suffice to say, I suspect this has more to do with the posh, catering to foreigners, type places he eats than a true reflection of the heat in SL curries.
Now I am the first to admit I do eat in the odd posh, catering to foreigners type of places from time to time. Usually when someone else is paying though ;-) The bulk of my experience though comes from eating in the works canteen, and eating lunch packets bought off stalls at the side of the road. However, I would be interested in any recommendations for typical Sri Lankan restaurants in and around Colombo. The best I have found is the Palmyrah Restaurant, which is certainly a tad up market and seems to have been closed now for around 9 months.
Lunch packets are basically a meal, traditionally mainly rice with a variety of choices of curry as accompanyment. The food is parcelled up in a packet (hence the name) and is usually sold by vendors at the side of the roads. Traditionally you eat the food with your hands. These can make for an interesting and certainly cheap meal. Around 50-100 rupees seems to be a typical price although this can rise if you go for the executive luch packets. So far I've not had a bad experience eating one of them.
At Crystal Martin in Sri Lanka we provide three free meals a day for our workers and so we have a pretty large canteen to cope with the 800ish workers we have. Although I have never been for breakfast or late afternoon lunch (purely because I'm not really hungry at those times) I have had many meals in the canteen at lunchtime. The lunchtime meal is self service and consists of rice, a few vegatable curries, a fish or chicken curry, sambol and usually something like a curried egg. The food is variable but does tend to be the eqivilant of English medium to hot and the menu does not appear to vary much week to week. I remember when I first arrived in Sri Lanka and ate in the canteen it did seem to cause quite a stir and I was constantly being quizzed about what I thought of the food. However, that all stopped one day about a month or so after I arrived. That lunchtime they served up a curry of English Vindaloo hotness. I usually don't sweat when I eat curry but this one even had beads of sweat appearing on my forehead. However, I wolfed it down and returned to the IT room contented. Shortly afterwards the other IT staff appeared and were curious to know what I thought of the food. When I said I thought it was a tad hot but had enjoyed it they couldn't believe it. Apparently they had sent theirs back because it was too hot! I think they realised at this point the Sri Lanka food was not a problem for me. Needless to say the only other ex-pat who eats in the canteen regularly is my boss and he is from Pakistan.
Now if you want a hot curry in Colombo I had recommend the Queen's Cafe, 417 R.A. De Mel Mawatha, Colombo 3. The Chicken Chettinad is particularly challenging and weighs in at around English Vindaloo standards. I chanced the Murg Tikka Masala tonight which was around an English medium curry strength. Excellent. A meal with rice and a parata will cost around 400 rupees to take away. The food usually takes between 15-30 minutes to prepare and always takes slightly longer than the staff say. The curries tend to be wet curries, i.e. curries with a sauce (called gravy over here), like English Indian curries (is that an oxymoron?), and not like Sri Lanka curries which tend to be dry. I have found only one other restaurant in Colombo that can compete on curry strength with the Queen's and its name eludes me at the moment but as I know where it is and as my wife is currently away in Kurunegala I may chance it before she gets back and post a review on my blog.
And just for the record when I am in England my favorite curries are either Jalfrezi, Vindaloo or Phaal (See Wikipedia Curry) For anyone into hot food there is nothing I have yet tasted that can match a good English Indian Phaal. Whether the Phaal's are the same in India I have no idea.