Getting Clean Telephone Numbers

I am working with a telephone list which has tens of thousands of rows of telephone numbers. My task is to clean up the data and make it ready foe SMS communications, so the data has
to be clean and correctly formatted. It needs to be in this format: 0125303681(no dashes, no spaces, no non-numeric data)

I have spent a few hours looking at the possible methods, and perhaps all roads lead to Rome, but the experts in this forum might see a better overall strategy.

My Method
Before modification the display value on a cell being examined is '012-5802043 and the actual cell value is the same, '012-5802043. Both have a leading apostrophe.

Step 1 - Find the ‘ symbol and replace with nothing (empty). Now the cell text is 012-5303681
Step 2 - Find the - symbol and replace with nothing (empty). Now the text is 125303681 (problem: the zero is now missing). Do same for other obvious junk (e.g. commas)
Step 3 - Use Format Cells > Custom. Type in ten zeros “0000000000” on the Type line. This will ensure every cell has a leading zero.
Result: 0125303681 is displayed in the cell. Some progress has been made √

Problem 1: The actual value is still ‘0125303681 (with the apostrophe) and this could be a problem after the CSV export (not sure, but it concerns me).
Problem 2: The above method works well enough on mobile numbers, but it adds redundant leading zeros to fixed lines (e.g. 78242000 becomes 0078242000). Whilst not a problem for SMS dialing, it could raise a problem for outbound calls at call center.

QUESTIONS
(1) Instead of Step 1, I could multiply each cell by 1 (e.g. A2*1) or use the Clean function ( Clean (A2) ) copied into an adjacent cell and then convert the column to values. Is this a better approach? Pros and Cons? (But it seems this method still introduces the leading apostrophe symbol though)

(2) Is there any point in converting the text to numbers at some stage?

(3) As there could be other types of junk data in there (e.g. !, ext, NA) I haven’t spotted (too many rows to view individually), what function would I use to search filter out non-numerical data so I can strip out everything except the actual numbers/integers?

(4) Finally, how do I pull down a cell (with an applied formula) all the way to the bottom of the column when there are numerous spaces (which must remain) in between? Normally you just double-click on the bottom-right header cell and it populates the entire column, but if there are spaces in between the auto fill will stop.

Thank you in advance. I will be buzzed if someone can appraise this strategy, or suggest a better one to solve this.

Examples of telephone data:
'012-5802043
012-333,4444
0124445555
125556666
000
NA
(empty cell)
'072510488
0000000000