So it sounds like you are doing the right kind of things (I guess you are doing the exercises you describe regularly?) to keep you burning calories.
One thing that come through in your writing seems to be that you are not really sure what you are burning in calories. This site (and plenty of others) have ways of calculating the calories you actually burn in each of your activities. Just like you might keep a food diary, you should keep an exercise diary too, just to make sure you know all calories in and out. Be really strict about counting everything in and out for 2-3 weeks. If you are still not losing anything (assuming a calorie deficit), take this information to your doctor because at that point you are breaking the laws of thermodynamics.
Sure, BMR is only calculating what you need to lie in bed all day. What you describe as your typical activity level would typically be equated with a 1.2x multiple (look up the Harris Benedict Equation) so you would need to consume 1800 calories to maintain the same weight. Adding your activities to this should result in weight loss but only if:
You are accurate about your calorie counting (50% of people underestimate).
You are exercising regularly (doing the things you describe)
The fact that you are not continuing to gain weight does not suggest a medical issue (but you should not rule it out). Did this new weight gain happen on your abdomen only and do you have any abdominal discomfort/bloating?
17 pounds of fat cannot happen overnight - it would break the laws of physics (it would require 59,500 calories to create that much fat - weight can be gained quickly through water retention though.
This next paragraph is going to sound harsh and you might decide to never respond to me again... but here goes anyway...
Your comments about the being unable to live a healthy lifestyle in the UK are frankly just excuses. If you really wanted to, you would find foods you can eat - there are fresh vegetables and fruit, eggs, milk and other goods that can be bought just as you can in the US. If you only ever eat pre-packaged/processed foods and cannot find them in the UK - perhaps this is the issue. Your boss's kitchen is not the issue - you can make space if you really wanted too. There are a thousand exercises that need no equipment - just body weight and a pair of sneakers. The area around Windsor is a great place to get outside and run! The weather is getting better and the evenings are getting longer.
That was meant as a helpful reflection - please don't be offended, just take it as a different point of view.
In order for me to lose weight, I have had to buy different things in the supermarket, things I had not previously tried, some I liked some I didn't. I will not resort to frosted cereals, hot chocolate and snacks - they don't fit into my calorie limits. I find other things, I experiment, I throw stuff away that I hate and keep the stuff I like. You seem determined to lose this weight, you should apply that determination to making your time away from home happy and healthy rather than depressing.
Began - March 10th 2010
Starting wieght 195.4lbs
Starting Body Fat 27.1%
Starting BMI 27.2
Target Weight 170
Target Body fat <19%
Target BMI 24
As of May 12th
Weight: 178 (Total lost 17.4
,Loss this week 2.0
Fat %: 22.3