What to do if Fiance visa is not approved??

[Terpe]

So not looking good for my application in terms of my Chas ISA.

Is there a particular amount for the FIance Visa I need to have in terms of cash or a certain amount of weeks at a certain amount?

Guess I could still appeal it though if it is rejected?

Yes and no. Currently there is no requirement (rule) about savings.
The key is have a regular amount of income for non-discretional expenditure based on income support levels.

The new financial rules also do not stipulate savings, only gross income.

Current income support level is £111.45 per week

So your qualifying (discretional income) will be Net Income minus rent/mortgage, council tax and any loan repayments from your income
For a couple with no children you need to have £111.45 left per week to satisfy the adequate maintenance requirement.

If you have more than more than £111.45 left per week (that is £482.95 per month = £111.45 x52 divide by 12), then you will fulfil the requirement.

Having said that, it's not unreasonable for the ECO to expect to see around £1500 as available savings in order to support air ticket costs to UK and out-of pocket settle-in expenses. But that's not a stipulated requirement.