Hi folks,
Here are some alternatives to consider in London.
(1) Instead of going to Oxford Street for shopping (which I consider far too touristy and crowded), consider Westfield London instead. It is served by at least three tube stations: Wood Lane, Shepherd's Bush, and Shepherd's Bush Market. It's entirely covered, so a great place to shop, rain or shine. And it's HUGE. I mean, HUGE. You really do not need to go anywhere else (except perhaps Bicester Village).
(2) Instead of buying the Oyster card, consider using any SG-issued contactless credit or debit card instead. You will also benefit from daily and weekly caps as long as you always use the same card to tap in and out. As long as your credit or debit card supports contactless payments, it will work. There is no need for any pre-registration even for foreign cards.
I've tested it with my SG AMEX Platinum contactless card; I know other people have used it with their POSB contactless cards. This saves you the trouble of buying the oyster card, making sure that there is enough balance, and returning it for a refund. Literally, just touch and go. Works on tube trains, buses, and most likely all other forms of public transport in London.
(3) Instead of taking the Heathrow Express or Heathrow Connect, consider using the London tube to travel in between London and Heathrow Airport. It is by far the cheapest way to do so, and prices start from GBP 3 per person. The Picadilly line brings you to Central London in about an hour. Great if you are on a budget and not in a hurry.
Do bear in mind that if you have heavy luggage, most of the train stations were constructed in the day when there were no such thing as lifts and escalators. So, expect to struggle over steps.
(4) Instead of bemoaning the lack of cheap hawker food (seriously, how do you have open air hawker centers in winter... please use some brains can? LOL), consider all the cheap and tasty ready-to-eat products in supermarkets. If you have cooking facilities in your accommodation, even better.
From salads to sandwiches to pizzas to beef bourguignon to scottish mussles in white wine cream sauce to desserts (the range is endless), you will be spoilt for choice. Just head to any supermarket. M&S is our favourite in terms of price and quality, but Waitrose is fairly decent too, and you can't really go wrong with any of the other famous supermarkets (Sainsburys, Tesco, Asda, Morrisons).
If you're on a tight budget, consider the german discounters: Aldi and Lidl. There's a reason why they're doing so well in the UK; their food is cheap AND good.
(5) Instead of activating data roaming, consider instead giffgaff SIM cards. I believe you can order them in advance and have them delivered to your address in SG. Typically, a goodybag is what you should be buying.
An added advantage of this SIM card is that it can be used anywhere in the EU once you have stayed in the UK for a minimum of three days. When that happens, EU Roaming is automatically turned on, which means you can then use your goodybag allowance anywhere in the EU without incurring roaming charges at all, as if you are still in the UK. What that means effectively is that you can roam for free in the EU, once you spend at least three days in the UK.
To elaborate; say you bought the GBP 12 goodybag which gives you 4GB data. Say you use 1GB in UK. You can use the other 3GB in any EU country within the one month validity of the goodybag.
To order your giffgaff SIM:
https://www.giffgaff.com/support/sim-and-number/ordering-your-first-sim
Hope this helps.