Corrected version:

It can be seen that the percentage of participation by them increased by the end. 

Explanation: 

The verb "was" is unnecessary in this sentence. "Increased" is the correct past tense form of the verb "increase."

Improved version:

It is clearly evident that the participation of women in senior management roles increased significantly over the given time period.

Corrected version:

Turning to the first two years, only 3% of women participated in Eldan Ltd as senior managers, while Bamforth Ltd recorded 9% and 11% during the period. 

Explanation: 

 The phrase "as a senior manager" should be "as senior managers" to match the plural noun "women." Also, the phrase "recorded with" should be changed to "recorded" to improve clarity.

Improved version:

In the initial two years, only 3% of women held senior management positions in Eldan Ltd, while Bamforth Ltd had participation rates of 9% and 11% during the same period. 

Corrected version:

However, the percentage of participation in Finsbury Ltd fell by 2% in 1980. 

Explanation: 

The phrase "in Finsbury Ltd" should be moved to the end of the sentence to improve clarity and flow. 

Improved version:

However, Finsbury Ltd experienced a 2% decrease in female participation in 1980.

Corrected version:

The percentage recorded more than a quarter in 1999, which was double that of 1985, for Eldan Ltd. 

Explanation: 

The word "doubled" should be changed to "double" to match the comparative form of the adjective "quarter." Also, the phrase "than that of" should be changed to "that of" to improve clarity.

Improved version:

By 1999, the percentage of women in senior management roles at Eldan Ltd had more than doubled compared to 1985, reaching over a quarter. 

Corrected version:

No Errors.

Improved version:

Similarly, Bamforth Ltd also saw a 2% increase, from 13% to 15%.

Corrected version:

Regarding 2015, 64% of women participated in Eldan Ltd, which was only 3% in the starting period. 

Explanation: 

The company name "Elden Ltd" should be corrected to "Eldan Ltd" for consistency.

Improved version:

In 2015, a remarkable 64% of women held senior management positions in Eldan Ltd, a significant increase from the initial 3%. 

Corrected version:

The percentage of women participating in Bamforth Ltd increased and stood at 46% by 2015.

Explanation: 

The phrase "participated for" should be changed to "participating in" to match the correct verb form. Also, the company name "Bamford Ltd" should be corrected to "Bamforth Ltd" for consistency. 

Improved version:

Similarly, Bamforth Ltd had a participation rate of 46% by 2015. 

Corrected version:

However, it was a fluctuating trend for Finsbury Ltd over the 40 years. 

Explanation: 

The adjective "fluctuent" should be changed to "fluctuating" to match the correct form.

Improved version:

In summary, the trend of women occupying senior management positions showed a consistent upward trajectory for both Eldan Ltd and Bamforth Ltd. However, Finsbury Ltd experienced fluctuating levels of female participation over the 40-year period.