Wait a bit or move now?

The market has been pretty stagnant throughout the time you have had the house and although the market is now starting to move again there are one heck of a lot of houses' out there waiting for a buyer. My feeling is that at the moment there are still far more homes available for sale than buyers so although you may not get more than you paid for the house and you will have the purchase costs associated with a new buy, including stamp duty, once that back log clears there could be rapid increases in price. So, on balance, i think that if i were in your position i would sell now rather than later particularly as you are going for something a bit more expensive. Yes your house would go up the same as others but the increase in value in your present house would amount to less than the increase in value of a bigger one so you would have to pay a lot more for a fairly modest upgrading. Sell it.

In some areas the market is rising, I don't know where you are. You should ask an Estate Agent for a valuation. You might be stung with early redemption fees from your Lender, and you will have to apply for a new mortgage. These costs could outweigh any profit you might make.

UK

Very unlikely that the numbers will work out the way you think they will. Usually it takes 5 years just to be ahead on the cost of selling and buying a house.

Why not use your spare cash money to upgrade what you have? Attic conversions and rear extensions can make a big difference to the amount of usable space and you can always modernise an older house. No need to do everything at once.