I've been @ - summoned! I'm an actuary but pension scheme transfer values are a technical area that are not in my field, although I'm aware of the main principles.
I guess we would expect a TV to reflect two amounts: what it would be expected to cost the pension scheme to provide your retirement benefits; what it should cost the transferring member to set up their own assets to provide their retirement benefits. These two figures will probably not be the same, and some poor actuary (yes, have pity) has to come up with a suitable calculation methodology for TVs that is fair to the employer and to the employee.
You would expect TVs to come down in value as gilt / bond yields go up (as they have been all year and accelerated recently), because you need to buy fewer assets (bonds - whether issued by government or companies) to generate the same return. However, @scrivette's reply points to a potential issue - a lag in the basis of calculation - so if the yields being used in the calculation are higher than current yields, the TV might look lower than you really want.
But the big concept we haven't mentioned is risk : if you stay in a DB scheme, the scheme carries all the investment and longevity risk - if the stockmarket falls, or yields fall (and you haven't matched assets to the liabilities) or inflation rises, or if members live longer than the scheme actuaries predicted (they try, but it's hard to get it right for the next 20, 30, 40 years), the employer ultimately bears the cost (with the insurance of the PPF if they go bust).
If you transfer out, then you are taking the risk on yourself (up to the point you choose to buy an annuity which transfers the risk to an insurer, but that could me many years in the future and will reflect the "price" of the risk when you retire, not its price now).