OK, let's not panic. Here is what you can do with NatWest.
You are an existing customer, so you can look at their remortgage rates here:
https://www.natwest.com/mortgages/mortgage-rates.html
You will see that you can get a 4.10% tracker for two years at a cost of £995 with an LTV of 60%.
The cheapest rates you can get for no fee are:
4.65% but you will need an LTV of 60%
4.75% with an LTV of 75%.
These are public rates, you may get better rates if you login to Manage My Mortgage.
We remortgaged last summer at 0.5% above base and we were expecting interest rates to fall quite significantlly this year. However, the Iran war changed things, but despite these shocks, the Bank of England has held interest rates at 3.75%. It is hard to see interest rates going up a lot in the next year unless something else unpredictable happens.
The measures taken by this government should get the economy moving in the next year and I think rates may fall gradually as a result.
You do not have to do anything until next year and at your current rate you should not remortgage immediately.
Without knowing your exact details, LTV and how many years are left on the mortgage term, it's hard to predict exact amounts. But you do have options. As a guideline, when I had a mortgage in 2003, the rate was 1% above base rate. The base rate was 6% and the rate would switch to 2% above base after a few years. My advisor said that I should switch to a better rate at that point. However, the base rate fell to about 0.5% so I was happy paying 2.5% when the time came. I'm saying this because it's a good rule of thumb, a tracker at no more than 1% above base (lower if possible) is really good value, even when interest rates are high.
Fixes are at 6%, so go for a tracker. You will be ok, you just need more information.