|The arms of Baron Petre|
Regency sites the world over like to claim there were no Catholic lords or gentry during the English Regency because Catholics couldn't inherit land or titles. This is not true. The 1791 Roman Catholic Relief Act removed many of the restrictions on Catholics, including their ability to inherit, but even before 1791 there were Catholic lords who had been Catholic on and off since the reign of Elizabeth. These were admittedly very few, but they did exist. Sir Henry Englefield, the 12th Duke of Norfolk, and his son-in-law Lord Petre (see description below) were among them. Also, the Irish peers, who could own land in England, had some influence on the English Catholic world (e.g. the Earl of Fingall owned property in Woolhampton, Berkshire, which they gave over to be used as a mission.)
We must consider too that the requirement to take the Oath of Supremacy, was often times temporarily abrogated (the deadline in which the oath was required to be taken was pushed back) by an act of Parliament. That did not mean, however, that Catholic peers could sit in parliament, or hold civil or military office. The Oath of Supremacy was required on certain occasions in these professions and thus, Catholics who held their faith were essentially prohibited from holding these offices.
Monetarily, the fact of their Catholicism had deep ramifications. They were required to pay double land taxes. Prior to the 1791 laws, steep fines could be applied for giving their children a Catholic education, or hearing Mass, but typically, unless one was convicted of breaking the law, the state would turn a blind eye.
The fact of their faith did not prevent them from funding chapels and schools. During the Regency, there were a series of mission chapels throughout the country, financed by wealthy patrons. While these patrons were sometimes those who had made their way in trade up North, others were Catholic lords, and even others were lapsed Catholics who still maintained a Catholic chapel (e.g. the 11th Duke of Norfolk who was reconciled to the faith on his deathbed).
Source: Dawn of the Catholic Revival, Bernard Ward